Adjust testcase for O2 vect.

Adjust testcase for O2 vect.

Adjust code in check_vect_slp_store_usage to make it an exact
pattern match of the corresponding testcases.
These new target/xfail selectors are added as a temporary solution,
and should be removed after real issue is fixed for Wstringop-overflow.

gcc/ChangeLog:

	* doc/sourcebuild.texi (vect_slp_v4qi_store_unalign,
	vect_slp_v2hi_store_unalign, vect_slp_v4hi_store_unalign,
	vect_slp_v4si_store_unalign): Document efficient target.
	(vect_slp_v4qi_store_unalign_1, vect_slp_v8qi_store_unalign_1,
	vect_slp_v16qi_store_unalign_1): Ditto.
	(vect_slp_v2hi_store_align,vect_slp_v2qi_store_align,
	vect_slp_v2si_store_align, vect_slp_v4qi_store_align): Ditto.
	(struct_4char_block_move, struct_8char_block_move,
	struct_16char_block_move): Ditto.

gcc/testsuite/ChangeLog:

	PR testsuite/102944
	* c-c++-common/Wstringop-overflow-2.c: Adjust target/xfail
	selector.
	* gcc.dg/Warray-bounds-48.c: Ditto.
	* gcc.dg/Warray-bounds-51.c: Ditto.
	* gcc.dg/Warray-parameter-3.c: Ditto.
	* gcc.dg/Wstringop-overflow-14.c: Ditto.
	* gcc.dg/Wstringop-overflow-21.c: Ditto.
	* gcc.dg/Wstringop-overflow-68.c: Ditto
	* gcc.dg/Wstringop-overflow-76.c: Ditto
	* gcc.dg/Wzero-length-array-bounds-2.c: Ditto.
	* lib/target-supports.exp (vect_slp_v4qi_store_unalign): New
	efficient target.
	(vect_slp_v4qi_store_unalign_1): Ditto.
	(struct_4char_block_move): Ditto.
	(struct_8char_block_move): Ditto.
	(stryct_16char_block_move): Ditto.
	(vect_slp_v2hi_store_align): Ditto.
	(vect_slp_v2qi_store): Rename to ..
	(vect_slp_v2qi_store_align): .. this.
	(vect_slp_v4qi_store): Rename to ..
	(vect_slp_v4qi_store_align): .. This.
	(vect_slp_v8qi_store): Rename to ..
	(vect_slp_v8qi_store_unalign_1): .. This.
	(vect_slp_v16qi_store): Rename to ..
	(vect_slp_v16qi_store_unalign_1): .. This.
	(vect_slp_v2hi_store): Rename to ..
	(vect_slp_v2hi_store_unalign): .. This.
	(vect_slp_v4hi_store): Rename to ..
	(vect_slp_v4hi_store_unalign): This.
	(vect_slp_v2si_store): Rename to ..
	(vect_slp_v2si_store_align): .. This.
	(vect_slp_v4si_store): Rename to ..
	(vect_slp_v4si_store_unalign): Ditto.
	(check_vect_slp_aligned_store_usage): Rename to ..
	(check_vect_slp_store_usage): .. this and adjust code to make
	it an exact pattern match of corresponding testcase.