Move n bytes from dst_offset to src_offset

Property definitions

c $ NativeCByteArray :: move
	# Move `n` bytes from `dst_offset` to `src_offset`
	fun move(dst_offset, src_offset, n: Int) `{
		memmove(self+dst_offset, self+src_offset, n);
	`}
lib/c/c.nit:204,2--207,3