setexit -> setjmp, reset -> longjmp, isdir() -> S_ISDIR, ANSI

setexit -> setjmp, reset -> longjmp, isdir() -> S_ISDIR, ANSI
Prof. Graham requested semantic changes to #defines in sh.h, removing the
last vestiges of the PWB/V6 shell

SCCS-vsn: bin/csh/csh.c 5.19
SCCS-vsn: bin/csh/err.c 5.4
SCCS-vsn: bin/csh/exec.c 5.9
SCCS-vsn: bin/csh/exp.c 5.5
SCCS-vsn: bin/csh/func.c 5.13
SCCS-vsn: bin/csh/glob.c 5.12
SCCS-vsn: bin/csh/csh.h 5.9
SCCS-vsn: bin/csh/init.c 5.6
SCCS-vsn: bin/csh/lex.c 5.9
SCCS-vsn: bin/csh/parse.c 5.5
SCCS-vsn: bin/csh/proc.c 5.14
SCCS-vsn: bin/csh/sem.c 5.10