Fluidsim - Restoring simulation speed control (ZanQdo request)

This commit restores support for freezing or speeding up physics sims. Animate
the "Speed" parameter under Domain->Time, which controls a multiplier factor for
the rate at which the sim proceeds (i.e. the old "Fac-Tim" setting).

Notes:
* Subversion bumped to 4 to patch up defaults for new value so that old sim
files will still run correctly
* Names/descriptions could do with some tweaking
* Porting this across was not that obvious since quite a bit of stuff had
changed (as in, been cleaned up). However, from tests so far, it seems to work
well.

source/blender/modifiers/intern/MOD_fluidsim_util.c

@@ -95,6 +95,7 @@ void fluidsim_init(FluidsimModifierData *fluidmd)
 
 		fss->animStart = 0.0; 
 		fss->animEnd = 4.0;
+		fss->animRate = 1.0;
 		fss->gstar = 0.005; // used as normgstar
 		fss->maxRefine = -1;
 		// maxRefine is set according to resolutionxyz during bake