Add GL_OES_EGL_image_external.  Includes new keyword, type, name mangling, built-in function calls, etc.


git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@24007 e7fa87d3-cd2b-0410-9028-fcbf551c1848