BUG: Fix/cleanup custom commands and custom targets. Make empty comment strings work. Fix ZERO_CHECK target always out of date for debugging. Fix Makefile driving of custom commands in a custom target. Fix dependencies on custom targets not in ALL in VS generators.

Source/cmMakefileLibraryTargetGenerator.h

@@ -23,6 +23,8 @@ class cmMakefileLibraryTargetGenerator:
   public cmMakefileTargetGenerator
 {
 public:
+  cmMakefileLibraryTargetGenerator();
+
   /* the main entry point for this class. Writes the Makefiles associated
      with this target */
   virtual void WriteRuleFiles();