Add support for OpenGL ES 3.2 features and shader constants

Add support for OpenGL ES 3.2 features and shader constants

- Shaders are generated with the version string
  appropriate for the running context version.
- Add tests for tessellation shader constants:
  - gl_MaxTessControlImageUniforms
  - gl_MaxTessEvaluationImageUniforms
  - gl_MaxTessControlAtomicCounters
  - gl_MaxTessEvaluationAtomicCounters
  - gl_MaxTessControlAtomicCounterBuffers
  - gl_MaxTessEvaluationAtomicCounterBuffers
- Validate corresponding extension support
  for the running context.

Change-Id: Ie11f610a2f7de35b31b9f0b4df31d8af5ca986fe