TestGearsES2SWT: Fix NPE
Fix GLVersionNumber (Bug 679): Don't use a subsequent version number if not valid!
Relax GLContextImpl.setGLFunctionAvailability(..)'s Version Matching if testing major < 3 versions. (Bug 679)

On OSX, we 'only' support the ctx ARB creation and hence have no !ARM fallback.

If querying a version [2.0 .. 3.0] for GL2, it is acceptable if a valid OpenGL version is lower, e.g. 1.4.