Support GLES in internal shaders and Vulkan software clip distance fallback

[Shivansps]

1. Added conditional presicion quantifiers
2. Implement software varying clip distance fallback for GLES and Vulkan
3. Removed usage glBindFragDataLocation() for both GL and GLES now all fragOutN use location=N in shader.
4. Vulkan will now export "#define USE_HW_CLIP_DISTANCE" as a shader header if clip distance features are availible.
5. Fixed int/float operations that GLES rejects

[qazwsxal]

re: envmap I don't think outColor is actually used, so try deleting that line