Revert "fix memmove my implementation"

This reverts commit 9e1ccc345fcdea782be986efb46236de9f791472, which appears
to be broken (see issue #24).

Conflicts:
	libc/string.c
Restore memset and fix memmove
Merge pull request #25 from ComputerNerd/moreLibc

Re-add memmove; this version is claimed to actually work.

Revert mistakenly removed memset, which is also re-added.
Merge remote-tracking branch 'upstream/master'