Make the PP report an error on undefined macro in "#if ..." for ES profiles, unless relaxed error checking is requested.  Still works as normal CPP on non-ES.

Also, improved error reporting in general for the PP.


git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@21417 e7fa87d3-cd2b-0410-9028-fcbf551c1848