Activated the multi-threaded rendering for the external software renderer.

git-svn-id: http://jpcsp.googlecode.com/svn/trunk@3678 4ab978e6-3352-0410-996c-0b42db0051c8
Do not crash for small bezier patch

git-svn-id: http://jpcsp.googlecode.com/svn/trunk@3679 4ab978e6-3352-0410-996c-0b42db0051c8