meson: add vlc and winstore option/fixes

• Disable vlc binary with -Dvlc=false
• Build for winstore with -Dwinstore_app=true
• Fix some libvlccore sources/libs for winstore

Some caveats:

• Should -Dwinstore_app=true and -Dvlc=true result in an error? Since the main binary isn't (and can't, afaict) be built for winstore anyway.
• The winstore check is now done inside the mingw check, mirroring configure.ac. Not sure if this is the best place for it, since clang-cl can also build (!3066 (merged)).

Also, it requires meson 0.63 to add libraries to the project globally (like done here)