Include necessary headers in commands

Source/cmAddCustomCommandCommand.h

@@ -3,8 +3,14 @@
 #ifndef cmAddCustomCommandCommand_h
 #define cmAddCustomCommandCommand_h
 
+#include <cmConfigure.h>
+#include <string>
+#include <vector>
+
 #include "cmCommand.h"
 
+class cmExecutionStatus;
+
 /** \class cmAddCustomCommandCommand
  * \brief cmAddCustomCommandCommand defines a new command (rule) that can
  *  be executed within the build process