Re-applies changes from Mantis #3734 to Util.cs and g_player_cs removed be recent  merge
Fixing screen saver kicking in during playback
When resetting the idle timer for a screen saver the msg.Result needs to be 1 to tell Windows to abort the request of SC_SCREENSAVE. But when base.WndProc() is called, this result is overwritten. Added a switch to abort WndProc() in case WM_SYSCOMMAND wants to abort the sceensaver.

In a log term solution the current organization of WndProc() needs to be revisited and the decision to call WndProc() from base, pluginmanager or other parts of MP better organized.