OpenGL ES CTS 3.2.4.0

New tests:

• Tests for EXT_texture_filter_anisotropic
• Tests for EXT_polygon_offset_clamp
• Tests for KHR_parallel_shader_compile
• Tests for KHR_no_error
• Tests for exposed extensions
• Tests for integer literal corner cases
• Tests for shader constant expression tests
• Tests for unsized array of atomic_uint
• Tests for transform feedback in separable program objects
• Tests for API limits
• Tests for cube map array support for ETC2

Improvements:

• Remove vsnprintf from OpenGL CTS
• Move robustness tests to custom context package
• Move context flags tests to custom context package
• Add new package for tests with no default context

Fixes:

• Fix uniform location use in robust_buffer_access
• Fix tessellation tests do not test undefined tessLevel inputs
• Accept compiler or link error as passing result
• drawCall error optional if beginXFB failed