Invoke ST_doPaletteStuff every game tic, not every frame

[JNechaevsky]

Same as described and done in fabiangreffrath/woof#1316. Few remarks:

• Heretic have void SB_PaletteFlash(void) in p_local.h. Kept it there for smaller diff, so no static declaration.
• Hexen handles F11 just a very little bit different, so call for SB_PaletteFlash(true) is still needed in mn_menu.c
• Maybe add some comments?

[fabiangreffrath]

Looks good, thank you!

[JNechaevsky]

Thanks! I was worried about Hexen calls with condition of consoleplayer like this one, but it's seems to be okay since SB_PaletteFlash itself is always referring to consoleplayer. But this PR does not improves multiplayer spy mode, as it was done for Doom already.