glsl: Add row_major field to glsl_struct_field

glsl: Add row_major field to glsl_struct_field

For now, this will always be false.  In the near future, an "interface"
type will be added that shares a lot of infrastructure with structures.

v2: Move row_major checking in glsl_type::record_key_compare from the
next patch to this patch.  Suggested by Paul Berry.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Carl Worth <cworth@cworth.org>
Reviewed-by: Paul Berry <stereotype441@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>