Fluid simulation manual number of threads option now doesn't set the number
of threads to the number of cores when the fluid is created. Rather it is now
set to 0 which means "use the number of threads specified for the scene".

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56942 954f8c5b-7b00-dc11-b283-0030488c597c