Fix filter/screenshake/flash update order

In 2.2, at render time, the game rendered screenshakes and flashes if
their timers were above 0, and then decremented them afterwards. The
game would also update the analogue filter right before rendering it,
too.

In 2.3, this was changed so the flash and screenshake timers were
unified, and also done at the end of the frame - right before rendering
happened. This resulted in 1-frame flashes and screenshakes not
rendering at all. The other changes in this patchset don't fix this
either. The analogue filter was also in the wrong order, but that is
less of an issue than flashes and screenshakes.

So, what I've done is made the flash and screenshake timers update right
before the loop switches over to rendering, and only decrements them
when we switch back to fixed functions (after rendering). The analogue
filter is also updated right before rendering as well. This restores
1-frame flashes and screenshakes, as well as restores the correct order
of analogue filter updates.

desktop_version/src/Graphics.h

@@ -156,6 +156,8 @@ public:
 
 	void render(void);
 	void renderwithscreeneffects(void);
+	void renderfixedpre(void);
+	void renderfixedpost(void);
 
 	bool Hitest(SDL_Surface* surface1, point p1, SDL_Surface* surface2, point p2);