Remove static variables from mball module

Moved all the static variables into a PROCESS
structure which is now passing all over to where
static variables used to be used.

There's still one static variable which is
cubetable, but it's being initialized once
and then used read-only. Maybe we'll need
to move cubetable initialization to blender
startup, but that could wait a bit for now.

For users it means BI rendered viewport
wouldn't crash when using metaballs.

--
svn merge -r57515:57516 ^/branches/soc-2013-depsgraph_mt



git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57517 954f8c5b-7b00-dc11-b283-0030488c597c