Use memcpy instead of memmove in __relocate_a_1

Use memcpy instead of memmove in __relocate_a_1

__relocate_a_1 is used to copy data after vector reizing.  This can be done by memcpy
rather than memmove.

libstdc++-v3/ChangeLog:

	PR middle-end/109849
	* include/bits/stl_uninitialized.h (__relocate_a_1): Use memcpy instead
	of memmove.