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/ir_function.cpp

@@ -66,7 +66,7 @@ parameter_lists_match(const exec_list *list_a, const exec_list *list_b)
 
       /* Try to find an implicit conversion from actual to param. */
       inexact_match = true;
-      switch ((enum ir_variable_mode)(param->mode)) {
+      switch ((enum ir_variable_mode)(param->data.mode)) {
       case ir_var_auto:
       case ir_var_uniform:
       case ir_var_temporary: