doccursor: expose cursor location

This is used to get the file name and line for error messages in the
parser. Naturally we need to expose it.

src/hawkmoth/doccursor.py

@@ -48,6 +48,10 @@ def meta(self):
             'cursor.spelling': self._cc.spelling,
         }
 
+    @property
+    def location(self):
+        return self._cc.location
+
     @property
     def comment(self):
         return self._comment.spelling if self._comment else None