Modernise the CMake build system slightly.

 - Update the version info
 - Don't expose a private header directory as public
 - Publish an exported target

With this, it's possible to just import the installed targets.  I have a
small overlay port for vcpkg on top of this that lets me import libucl,
which is a first step towards fixing vstakhov#254.

CMakeLists.txt

@@ -1,9 +1,9 @@
 PROJECT(libucl C)
-CMAKE_MINIMUM_REQUIRED(VERSION 2.6.0 FATAL_ERROR)
+CMAKE_MINIMUM_REQUIRED(VERSION 3.1.0 FATAL_ERROR)
 
 SET(LIBUCL_VERSION_MAJOR 0)
-SET(LIBUCL_VERSION_MINOR 5)
-SET(LIBUCL_VERSION_PATCH 0)
+SET(LIBUCL_VERSION_MINOR 8)
+SET(LIBUCL_VERSION_PATCH 1)
 
 SET(LIBUCL_VERSION
         "${LIBUCL_VERSION_MAJOR}.${LIBUCL_VERSION_MINOR}.${LIBUCL_VERSION_PATCH}")
@@ -237,9 +237,8 @@ ADD_LIBRARY(ucl ${LIB_TYPE} ${UCLSRC})
 ADD_LIBRARY(ucl::ucl ALIAS ucl)
 SET_TARGET_PROPERTIES(ucl PROPERTIES VERSION ${LIBUCL_VERSION} SOVERSION ${LIBUCL_VERSION_MAJOR})
 TARGET_INCLUDE_DIRECTORIES(ucl
-	PUBLIC
-	  include
 	PRIVATE
+	  include
 	  src
 	  uthash
 	  klib)
@@ -305,10 +304,16 @@ ENDIF(UNIX)
 SET_TARGET_PROPERTIES(ucl PROPERTIES
 	PUBLIC_HEADER "${UCLHDR}")
 
-INSTALL(TARGETS ucl DESTINATION ${CMAKE_INSTALL_LIBDIR}
+INSTALL(TARGETS ucl EXPORT uclConfig DESTINATION ${CMAKE_INSTALL_LIBDIR}
 		PUBLIC_HEADER DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 
 IF(ENABLE_UTILS MATCHES "ON")
     ADD_SUBDIRECTORY(utils)
 ENDIF()
 
+install(EXPORT uclConfig
+	FILE ucl-config.cmake
+	NAMESPACE ucl::
+	DESTINATION "share/ucl"
+)
+