/usr/include/baudboy.h should include fcntl.h because it uses open(). If you
don't first include fcntl.h, open() will get an implicit definition (which is
usually bad and won't compile).
I think this hasn't been noticed because current baudboy.h users include fcntl.h
themselves first. I'm building ckermit with baudboy.h and it doesn't include
fcntl.h, so it won't compile.