Add the GL_ES macro for ES personalities, along with a general mechanism for adding preambles in front of shaders without effecting line numbers, etc.


git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@21122 e7fa87d3-cd2b-0410-9028-fcbf551c1848