CodeBlocks: Declare which source file belongs to which targets.

This should allow the consuming IDE to determine which target specific
preprocessor definitions and include directories are relevant for a
given source file.

Source/cmExtraCodeBlocksGenerator.h

@@ -39,6 +39,10 @@ public:
 
   virtual void Generate();
 private:
+  struct CbpUnit
+  {
+    std::vector<const cmTarget*> Targets;
+  };
 
   void CreateProjectFile(const std::vector<cmLocalGenerator*>& lgs);