Precision type of vec4
http://www.khronos.org/bugzilla/show_bug.cgi?id=781

Fixed illegal default precision qualifier in large-loop-test and added tests of all valid and invalid default precision qualifiers in vertex and fragment shaders. Filed ANGLE bug 410 about the failure of the new tests.
Merge pull request #173 from kenrussell/precisions

Precision type of vec4