GLSL backend now emits "#version 120" to legally access invariant keyword and gl_PointCoord built-in variable.
BUG=35
Review URL: http://codereview.appspot.com/2341043

git-svn-id: https://angleproject.googlecode.com/svn/trunk@448 736b8ea6-26fd-11df-bfd4-992fa37f6226