pwdx by Lukasz Skalski.
Cleanup pwdx
Switch ls from utoa to sprintf.
Convert dhcp/dhcpd from utoa() to sprintf().
Remove itoa/utoa, let libc do this with sprintf.
Introduce libbuf analogous to toybuf but for use by lib/*.c. Change readfile() semantics to be able to read into an existing buffer, or malloc its own if that's NULL.
First pass at umount, not quite done yet.