Set fademode to temp 0 when going to in-game options

While I've decoupled fademode from gamemode starting, being faded out on
the title screen results in a black screen and you being unable to make
any input. So we'll need to store the current fademode in a temporary
variable when going to in-game options, then put it back when we return
to the pause menu. Yes, you can turn on glitchrunner mode during the
in-game options, and then immediately return to the pause menu to
instantly go back to the title screen; this is intended.

Due to frame ordering, putting the fademode back needs to be deferred to
the end of the frame to prevent a 1-frame flicker.

It's actually sufficient enough to do this temporary fademode storage to
fix the whole thing, but I also decided to decouple fademode and
gamemode starting just to be sure.

desktop_version/src/Graphics.cpp

@@ -98,6 +98,7 @@ void Graphics::init(void)
 
     setfade(0);
     fademode = 0;
+    ingame_fademode = 0;
 
     // initialize everything else to zero
     backBuffer = NULL;