glsl: Record in gl_shader_program whether the program uses GLSL ES.

Previously we recorded just the GLSL version (or the max version, if
GLSL 1.10 and GLSL 1.20 programs were linked together).

[v2, idr]: s/IsEs(Shader|Prog)/IsES/  Suggested by Ken and Eric.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Acked-by: Carl Worth <cworth@cworth.org>

src/glsl/linker.cpp

@@ -2463,6 +2463,7 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
    }
 
    prog->Version = max_version;
+   prog->IsES = is_es_prog;
 
    for (unsigned int i = 0; i < MESA_SHADER_TYPES; i++) {
       if (prog->_LinkedShaders[i] != NULL)