VS: Switch to internal CMAKE_MAKE_PROGRAM lookup by generators

Drop the "Modules/CMakeVS*FindMake.cmake" files.  Override the
cmGlobalGenerator::FindMakeProgram method for VS generators to use their
internal APIs to locate the build tool.  Set the CMAKE_MAKE_PROGRAM as a
normal variable for use by project code, but do not cache it.  This will
allow CMake and CTest to select the proper tool at build time.

Source/cmGlobalVisualStudio7Generator.h

@@ -173,6 +173,7 @@ private:
   char* IntelProjectVersion;
   std::string DevEnvCommand;
   bool DevEnvCommandInitialized;
+  virtual std::string GetVSMakeProgram() { return this->GetDevEnvCommand(); }
 };
 
 #define CMAKE_CHECK_BUILD_SYSTEM_TARGET "ZERO_CHECK"