uart.c cleanup
Rewrote os_strspn and os_strcspn

Replaced MUSL's version of strspn and strcspn because they were causing bugs
Moved functions around in klibc.c
Replaced size_t with os_size_t to avoid a naming conflict
Minor bugfixes
added os_memcpy for loader. If problems feel free to remove
fixed dumb bug for os_memcpy and also fixed up sloppy merging problems
Merge branch 'klibc' of https://github.com/rellermeyer/course_os into argparse

Conflicts:
	kernel/Makefile
	kernel/start.c