glsl: Hide many classes local to individual .cpp files in anon namespaces.

This gives the compiler the chance to inline and not export class symbols
even in the absence of LTO.  Saves about 60kb on disk.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@.intel.com>

src/glsl/link_varyings.cpp

@@ -597,6 +597,7 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
    return true;
 }
 
+namespace {
 
 /**
  * Data structure recording the relationship between outputs of one shader
@@ -689,6 +690,7 @@ private:
    const bool consumer_is_fs;
 };
 
+} /* anonymous namespace */
 
 varying_matches::varying_matches(bool disable_varying_packing,
                                  bool consumer_is_fs)