Several fixes/improvements:

- Fixed CollapseFullPath to work on relative paths with base paths
    not in the current working directory.
  - INCLUDE command now supports relative paths (using above fix).
  - Added ABSOLUTE option to GET_FILENAME_COMPONENT command to
    unwind symlinks and relative paths.
  - Fixed libName_EXPORTS macro definition to be valid C identifier.
  - Added DEFINE_SYMBOL target propterty for customizing the export symbol.
  - Implemented LINK_FLAGS target propterty for libraries in VC6 and VC7.

Several of these fixes were contributed by Gareth Jones.

Source/cmSetTargetPropertiesCommand.h

@@ -55,7 +55,11 @@ public:
       return
         "SET_TARGET_PROPERTIES(target1 target2 .. filen PROPERTIES prop1 value1 prop2 value2 ... prop2 valuen)"
         "Set properties on a target. The syntax for the command is to list all the files you want "
-        "to change, and then provide the values you want to set next.  Properties that cmake knows about are PREFIX and POSTFIX for Unix systems and libraries.   CMake also knows about LINK_FLAGS, which can be used to add extra flags to the link step of a target.   You can use and prop value pair you want and extract it later with the GET_TARGET_PROPERTY command.";
+        "to change, and then provide the values you want to set next.  Properties that cmake knows about are PREFIX and POSTFIX for Unix systems and libraries.   CMake also knows about LINK_FLAGS, which can be used to add extra flags to the link step of a target."
+        "DEFINE_SYMBOL is a symbol that is defined when compiling C or C++ sources.  "
+        "If not set here then it is set to target_EXPORTS by default "
+        "(with some substitutions if target is not a valid C identifier).  "
+        "You can use and prop value pair you want and extract it later with the GET_TARGET_PROPERTY command.";
     }
   
   cmTypeMacro(cmSetTargetPropertiesCommand, cmCommand);