testsute: Add expected warning for packed attribute

testsute: Add expected warning for packed attribute

Targets which pack structures by default get warnings for packed structure
attributes. This is expected, so add markers in the test cases.

gcc/testsuite/ChangeLog:

	* c-c++-common/Waddress-of-packed-member-2.c: Add dg-warning for
	ignored attribute if target is default_packed.
	* c-c++-common/Wattributes.c: Ditto.
	* c-c++-common/attr-copy.c: Ditto.
	* c-c++-common/builtin-has-attribute-4.c: Ditto.
	* c-c++-common/pr51628-29.c: Ditto.
	* c-c++-common/pr51628-30.c: Ditto.
	* c-c++-common/pr51628-32.c: Ditto.
	* gcc.dg/Wattributes-6.c: Ditto.
	* gcc.dg/attr-copy-4.c: Ditto.
	* gcc.dg/attr-copy-8.c: Ditto.

Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>