Extend the offset and size of merged object references [PR103215].

Extend the offset and size of merged object references [PR103215].

Resolves:
PR tree-optimization/103215 - bogus -Warray-bounds with two pointers with different offsets each

gcc/ChangeLog:

	PR tree-optimization/103215
	* pointer-query.cc (access_ref::merge_ref): Extend the offset and
	size of the merged object instead of using the larger.

gcc/testsuite/ChangeLog:

	PR tree-optimization/103215
	* gcc.dg/Wstringop-overflow-58.c: Adjust and xfail expected warnings.
	* gcc.dg/Wstringop-overflow-59.c: Same.
	* gcc.dg/warn-strnlen-no-nul.c: Same.
	* gcc.dg/Warray-bounds-91.c: New test.
	* gcc.dg/Warray-bounds-92.c: New test.
	* gcc.dg/Wstringop-overflow-85.c: New test.
	* gcc.dg/Wstringop-overflow-87.c: New test.