initial commit of the fluid simulator.

Ton reviewed and gave his blessing.
Zr, can you have a look ?

see :
http://projects.blender.org/tracker/?func=detail&atid=127&aid=3039&group_id=9

for initial comments.

N_T : the solver itself (elbeem) needs some works to get rid of
warnings

source/blender/include/butspace.h

@@ -234,6 +234,10 @@ void test_idbutton_cb(void *namev, void *arg2_unused);
 	/* this has MAX_EFFECT settings! Next free define is 1450... */
 #define B_SELEFFECT	1430	
 
+/* Fluidsim button defines */
+#define B_FLUIDSIM_BAKE	  1450
+#define B_FLUIDSIM_SELDIR	1451
+
 
 /* *********************** */
 #define B_WORLDBUTS		1600