Time to start reaping the benefits of code unification. Support for
pressure spacing across all paint systems (was supported only for
texture painting earlier). Also, switch paint code to use the new code
path from now on. No shift-Lclick required anymore.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55145 954f8c5b-7b00-dc11-b283-0030488c597c