a small implementation of memcpy(). libsa memcpy() wouldn't do the right thing if LIBSA_USE_MEMCPY was defined, and the whole point of that define is to get rid of either bcopy() or memcpy(). (cloned from the bcopy() code.)
it's really true...we didn't have one before, even though the Makefile thought we did. (Yes, I checked the Attic...)
