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

intern/SConscript

@@ -9,6 +9,7 @@ SConscript(['SoundSystem/SConscript',
             'memutil/SConscript/',
             'decimation/SConscript',
             'iksolver/SConscript',
+            'elbeem/SConscript',
             'opennl/SConscript'])
 
 NEW_CSG='false'