glsl parser: allow in & out for interface block members

glsl parser: allow in & out for interface block members

Previously uniform blocks allowed for the 'uniform' keyword
to be used with members of a uniform blocks. With interface
blocks 'in' can be used on 'in' interface block members and
'out' can be used on 'out' interface block members.

The basic_interface_block rule will verify that the same
qualifier type is used with the block and each member.

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>