Handle volatile array types in dwarf2read.c.

Handle volatile array types in dwarf2read.c.

read_tag_const_type propagates the cv-qualifier to the array element type,
but read_tag_volatile_type didn't. Make sure that both cv-qualifiers that
apply to array types are handled the same.

gdb/ChangeLog

	* dwarf2read.c (add_array_cv_type): New function.
	(read_tag_const_type): Call add_array_cv_type for TYPE_CODE_ARRAY.
	(read_tag_volatile_type): Likewise.

gdb/testsuite/ChangeLog

	* gdb.base/constvars.c (violent, violet, vips, virgen, vulgar,
	vulture, vilify, villar): New volatile array constants.
	(vindictive, vegetation): New const volatile array constants.
	* gdb.base/volatile.exp: Test volatile and const volatile array
	types.