PR libstdc++/77691 increase allocation size to at least alignment

PR libstdc++/77691 increase allocation size to at least alignment

It's not safe to assume that malloc(n) returns memory aligned to more
than n, so when relying on the guaranteed alignment of malloc ensure
that the number of bytes allocated is at least as large as the
alignment.

	PR libstdc++/77691
	* include/experimental/memory_resource (__resource_adaptor_imp): Do
	not allocate sizes smaller than alignment when relying on guaranteed
	alignment.
	* testsuite/experimental/memory_resource/new_delete_resource.cc:
	Adjust expected number of bytes allocated for alignof(max_align_t).

From-SVN: r265068