builtins.c (fold_builtin_memory_op): Optimize memmove into memcpy if we can prove source and destination don't overlap.

	* builtins.c (fold_builtin_memory_op): Optimize memmove
	into memcpy if we can prove source and destination don't overlap.

	* gcc.dg/memmove-2.c: New test.
	* gcc.dg/memmove-3.c: New test.

From-SVN: r145127