.gitignore update for VS2015 Update 2

Seems we may need a *.VC.db ignore added - apparently these replace the old sdf intellisense files as of VS 2015 Update 2.

I’ve got a recalcitrant file hanging around in the Projucer directory: extra\Projucer\Builds\VisualStudio2015\Projucer.VC.db

Done, thanks!