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/opt_structure_splitting.cpp

@@ -103,8 +103,8 @@ ir_structure_reference_visitor::get_variable_entry(ir_variable *var)
 {
    assert(var);
 
-   if (!var->type->is_record() || var->mode == ir_var_uniform
-       || var->mode == ir_var_shader_in || var->mode == ir_var_shader_out)
+   if (!var->type->is_record() || var->data.mode == ir_var_uniform
+       || var->data.mode == ir_var_shader_in || var->data.mode == ir_var_shader_out)
       return NULL;
 
    foreach_iter(exec_list_iterator, iter, this->variable_list) {