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/lower_vector.cpp

@@ -31,6 +31,8 @@
 #include "ir.h"
 #include "ir_rvalue_visitor.h"
 
+namespace {
+
 class lower_vector_visitor : public ir_rvalue_visitor {
 public:
    lower_vector_visitor() : progress(false)
@@ -48,6 +50,8 @@ public:
    bool progress;
 };
 
+} /* anonymous namespace */
+
 /**
  * Determine if an IR expression tree looks like an extended swizzle
  *