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/opt_dead_builtin_varyings.cpp

@@ -52,6 +52,7 @@
 #include "glsl_types.h"
 #include "link_varyings.h"
 
+namespace {
 
 /**
  * This obtains detailed information about built-in varyings from shader code.
@@ -397,6 +398,7 @@ private:
    ir_variable *new_fog;
 };
 
+} /* anonymous namespace */
 
 static void
 lower_texcoord_array(exec_list *ir, const varying_info_visitor *info)