I ran out of steam writing library routines and imported two
BSD-licensed libc routines: sscanf() and getopt().
I will most likely rewrite them sooner or later. For now
I just wanted to see figlet running.
I added a dead-simple malloc that only allows allocations < 4096 bytes.
It just forwards the request to mmap() every time.
I also added simplified versions of opendir() and readdir().