Fix #35054: adjust tooltip for Render Border option in 3D view panel to say
it has an effect outside of the camera view.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56207 954f8c5b-7b00-dc11-b283-0030488c597c
Attempt to fix #35041 and #34725: cycles crash with OSL and both a 3D viewport
and preview running at the same time.

It seems there's something in OSL/LLVM that's not thread safe, but I couldn't
figure out what exactly. Now all renders share the same OSL ShadingSystem which
should avoid the problem.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56208 954f8c5b-7b00-dc11-b283-0030488c597c