glsl: move variables in to ir_variable::data, part I

This patch moves following bitfields in to the data structure:

used, assigned, how_declared, mode, interpolation,
origin_upper_left, pixel_center_integer

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>

src/glsl/ast_array_index.cpp

@@ -168,7 +168,7 @@ _mesa_ast_array_index_to_hir(void *mem_ctx,
       if (array->type->is_unsized_array()) {
 	 _mesa_glsl_error(&loc, state, "unsized array index must be constant");
       } else if (array->type->fields.array->is_interface()
-                 && array->variable_referenced()->mode == ir_var_uniform) {
+                 && array->variable_referenced()->data.mode == ir_var_uniform) {
 	 /* Page 46 in section 4.3.7 of the OpenGL ES 3.00 spec says:
 	  *
 	  *     "All indexes used to index a uniform block array must be