Update SYNOPSIS for setkey() to show it's in <stdlib.h>
ok jmc@, millert@

rescinded 22 July 1999.  Proofed by myself and Theo.

All POSIX libc api now there (to P1003.1c/D10)
(more md stuff is needed for other libc/arch/*)
(setlogin is no longer a special syscall)
Add -pthread option to gcc (that makes it use -lc_r and -D_POSIX_THREADS).
Doc some re-entrant routines
Add libc_r to intro(3)
dig() uses some libc srcs and an extra -I was needed there.
Add more md stuff to libc_r.
Update includes for the pthreads api
Update libc_r TODO

Make sure everything uses {SYS,}LIBC_SCCS properly