[win32] Headerfiles/compiler settings cleanup

Headerfiles/compiler settings cleanup to stop msbuild rebuilding projects and files that haven't changed.

Fixes the following compile timesuckers:
* msbuild always builds projects with missing headerfiles even though no files have changed (libPlatinum, Kodi)
* msbuild rebuilds the entire project when there are duplicate compileroptions (Kodi release build configuration)
* msbuild always triggers custom build tools if the input or output file doesn't exist (git revision custombuild configuration in Kodi release build)