Use Windows themes for the Win32 GUI executables

This adds the necessary ComCtl manifests to allow the Win32 GUI executables to be styled using the system theme in Windows XP and later (at least until they are ported to a cross-platform toolkit).

Currently, I've enabled the following executables (let me know if I'm missing any):
- plClient
- UruLauncher
- plFontConverter
- plLocalizationEditor
- plResBrowser