Rename mplayer.*.{rc,po(t)} to mpc-hc.*.{rc,po(t)}.

Also use more appropriate language codes for the language DLLs.
PPageShaders: remove refactoring leftover

CID 1135355
Reposition toolbars properly on media close
Clear osd messages in CloseMedia()
Option to delay playback after mode auto-switch

Fixes #3235
Make use of mouse nav buttons in Playlist panel