lib: use std::move() where appropriate

Suggested by Coverity:
```
Error: COPY_INSTEAD_OF_MOVE:
src/lib/filter.cc:114:25: copy_constructor_call: "evt" is copied and then passed-by-reference as parameter to STL insertion function "std::vector<DefEvent, std::allocator<DefEvent> >::push_back(std::vector<DefEvent, std::allocator<DefEvent> >::value_type const &)", when it could be moved instead.
src/lib/filter.cc:114:25: remediation: Use "std::move(""evt"")" instead of "evt".

Error: COPY_INSTEAD_OF_MOVE:
src/lib/filter.cc:205:29: copy_constructor_call: "evt" is copied and then passed-by-reference as parameter to STL insertion function "std::set<DefEvent, std::less<DefEvent>, std::allocator<DefEvent> >::insert(std::set<DefEvent, std::less<DefEvent>, std::allocator<DefEvent> >::value_type const &)", when it could be moved instead.
src/lib/filter.cc:205:29: remediation: Use "std::move(""evt"")" instead of "evt".

Error: COPY_INSTEAD_OF_MOVE:
src/lib/parser-cov.cc:428:28: copy_constructor_call: "str" is copied and then passed-by-reference as parameter to STL insertion function "std::set<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >::insert(std::set<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >::value_type const &)", when it could be moved instead.
src/lib/parser-cov.cc:428:28: remediation: Use "std::move(""str"")" instead of "str".

Error: COPY_INSTEAD_OF_MOVE:
src/lib/parser-gcc.cc:552:46: copy_constructor_call: "evt" is copied and then passed-by-reference as parameter to STL insertion function "std::vector<DefEvent, std::allocator<DefEvent> >::push_back(std::vector<DefEvent, std::allocator<DefEvent> >::value_type const &)", when it could be moved instead.
src/lib/parser-gcc.cc:552:46: remediation: Use "std::move(""evt"")" instead of "evt".

Error: COPY_INSTEAD_OF_MOVE:
src/lib/parser-gcc.cc:558:46: copy_constructor_call: "evt" is copied and then passed-by-reference as parameter to STL insertion function "std::vector<DefEvent, std::allocator<DefEvent> >::push_back(std::vector<DefEvent, std::allocator<DefEvent> >::value_type const &)", when it could be moved instead.
src/lib/parser-gcc.cc:558:46: remediation: Use "std::move(""evt"")" instead of "evt".

Error: COPY_INSTEAD_OF_MOVE:
src/lib/parser-json-sarif.cc:205:13: copy_assignment_call: "uri" is copied in call to copy assignment for class "std::string const", when it could be moved instead.
src/lib/parser-json-sarif.cc:205:30: remediation: Use "std::move(""uri"")" instead of "uri".

Error: COPY_INSTEAD_OF_MOVE:
src/lib/parser-json-sarif.cc:250:32: copy_constructor_call: "evt" is copied and then passed-by-reference as parameter to STL insertion function "std::vector<DefEvent, std::allocator<DefEvent> >::push_back(std::vector<DefEvent, std::allocator<DefEvent> >::value_type const &)", when it could be moved instead.
src/lib/parser-json-sarif.cc:250:32: remediation: Use "std::move(""evt"")" instead of "evt".

Error: COPY_INSTEAD_OF_MOVE:
src/lib/parser-json-simple.cc:157:30: copy_constructor_call: "evt" is copied and then passed-by-reference as parameter to STL insertion function "std::vector<DefEvent, std::allocator<DefEvent> >::push_back(std::vector<DefEvent, std::allocator<DefEvent> >::value_type const &)", when it could be moved instead.
src/lib/parser-json-simple.cc:157:30: remediation: Use "std::move(""evt"")" instead of "evt".

Error: COPY_INSTEAD_OF_MOVE:
src/lib/parser-json-zap.cc:144:9: copy_assignment_call: "version" is copied in call to copy assignment for class "std::string const", when it could be moved instead.
src/lib/parser-json-zap.cc:144:49: remediation: Use "std::move(""version"")" instead of "version".

Error: COPY_INSTEAD_OF_MOVE:
src/lib/parser-xml-valgrind.cc:61:9: copy_assignment_call: "argVal" is copied in call to copy assignment for class "std::string const", when it could be moved instead.
src/lib/parser-xml-valgrind.cc:61:17: remediation: Use "std::move(""argVal"")" instead of "argVal".

Error: COPY_INSTEAD_OF_MOVE:
src/lib/parser-xml-valgrind.cc:227:32: copy_constructor_call: "noteEvt" is copied and then passed-by-reference as parameter to STL insertion function "std::vector<DefEvent, std::allocator<DefEvent> >::push_back(std::vector<DefEvent, std::allocator<DefEvent> >::value_type const &)", when it could be moved instead.
src/lib/parser-xml-valgrind.cc:227:32: remediation: Use "std::move(""noteEvt"")" instead of "noteEvt".
```

Related: #216

src/lib/filter.cc

@@ -111,7 +111,7 @@ void appendCtxLines(
         evt.event = "#";
         evt.msg = str.str();
         evt.verbosityLevel = /* not a key event */ 1;
-        pDst->push_back(evt);
+        pDst->push_back(std::move(evt));
     }
 }
 
@@ -202,7 +202,7 @@ bool DuplicateFilter::matchDef(const Defect &def)
     evt.fileName = MsgFilter::inst().filterPath(evt.fileName);
     evt.msg = MsgFilter::inst().filterMsg(evt.msg, def.checker);
 
-    return d->lookup.insert(evt)./* inserted */second;
+    return d->lookup.insert(std::move(evt))./* inserted */second;
 }
 
 

src/lib/parser-cov.cc

@@ -425,7 +425,7 @@ bool KeyEventDigger::guessKeyEvent(Defect *def)
         // no override for the checker -> match the lowered checker name
         std::string str(def->checker);
         boost::algorithm::to_lower(str);
-        defKeyEvent.insert(str);
+        defKeyEvent.insert(std::move(str));
     }
 
     // look for an explicitly defined key event

src/lib/parser-gcc.cc

@@ -549,13 +549,13 @@ bool BasicGccParser::getNext(Defect *pDef)
             case T_INC:
             case T_SCOPE:
                 done = this->exportAndReset(pDef);
-                defCurrent_.events.push_back(evt);
+                defCurrent_.events.push_back(std::move(evt));
                 break;
 
             case T_MSG:
                 done = this->exportAndReset(pDef);
                 defCurrent_.keyEventIdx = defCurrent_.events.size();
-                defCurrent_.events.push_back(evt);
+                defCurrent_.events.push_back(std::move(evt));
                 hasKeyEvent_ = true;
                 break;
 

src/lib/parser-json-sarif.cc

@@ -202,7 +202,7 @@ static void sarifReadLocation(DefEvent *pEvt, const pt::ptree &loc)
         const auto uri = valueOf<std::string>(*al, "uri");
         if (!uri.empty())
             // read file name
-            pEvt->fileName = uri;
+            pEvt->fileName = std::move(uri);
     }
 
     const pt::ptree *reg;
@@ -247,7 +247,7 @@ static void sarifReadComments(Defect *pDef, const pt::ptree &relatedLocs)
             continue;
 
         evt.verbosityLevel = 1;
-        pDef->events.push_back(evt);
+        pDef->events.push_back(std::move(evt));
     }
 }
 

src/lib/parser-json-simple.cc

@@ -154,7 +154,7 @@ bool SimpleTreeDecoder::readNode(Defect *def)
         if (-1 == evt.verbosityLevel)
             verbosityLevelNeedsInit = true;
 
-        evtListDst.push_back(evt);
+        evtListDst.push_back(std::move(evt));
     }
 
     // read "defect_id", "cwe", and "function" if available

src/lib/parser-json-zap.cc

@@ -141,7 +141,7 @@ void ZapTreeDecoder::readScanProps(
 {
     const auto version = valueOf<std::string>(*root, "@version");
     if (!version.empty())
-        (*pDst)["analyzer-version-owasp-zap"] = version;
+        (*pDst)["analyzer-version-owasp-zap"] = std::move(version);
 
     d->timeStamp = valueOf<std::string>(*root, "@generated");
 }

src/lib/parser-xml-valgrind.cc

@@ -58,7 +58,7 @@ bool /* continue */ skipLdArgs(
             goto skip_arg;
 
         // record path of the real binary being executed
-        *pExe = argVal;
+        *pExe = std::move(argVal);
         ++(*pIt);
         return /* continue */ (itEnd != *pIt);
 
@@ -224,7 +224,7 @@ void readStack(Defect *pDef, const pt::ptree &stackNode)
         }
 
         // finally push the "note" event
-        pDef->events.push_back(noteEvt);
+        pDef->events.push_back(std::move(noteEvt));
     }
 }