glsl: Implement ARB_texture_query_lod

v2 [mattst88]:
   - Rebase.
   - #define GL_ARB_texture_query_lod to 1.
   - Remove comma after ir_lod in ir.h for MSVC.
   - Handled ir_lod in ir_hv_accept.cpp, ir_rvalue_visitor.cpp,
     opt_tree_grafting.cpp.
   - Rename textureQueryLOD to textureQueryLod, see
     https://www.khronos.org/bugzilla/show_bug.cgi?id=821
   - Fix ir_reader of (lod ...).
v3 [mattst88]:
   - Rename textureQueryLod to textureQueryLOD, pending resolution of
     Khronos 821.
   - Add ir_lod case to ir_to_mesa.cpp.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/glsl/ir_print_visitor.cpp

@@ -278,6 +278,7 @@ void ir_print_visitor::visit(ir_texture *ir)
    switch (ir->op)
    {
    case ir_tex:
+   case ir_lod:
       break;
    case ir_txb:
       ir->lod_info.bias->accept(this);