include file pass, csh.h no longer include every .h in the system

include file pass, csh.h no longer include every .h in the system
rename sigmast_t to sigset_t to match signal.h; minor pointer cleanups

SCCS-vsn: bin/csh/Makefile 5.22
SCCS-vsn: bin/csh/csh.c 5.25
SCCS-vsn: bin/csh/csh.h 5.15
SCCS-vsn: bin/csh/dir.c 5.9
SCCS-vsn: bin/csh/dol.c 5.12
SCCS-vsn: bin/csh/err.c 5.9
SCCS-vsn: bin/csh/exec.c 5.15
SCCS-vsn: bin/csh/exp.c 5.10
SCCS-vsn: bin/csh/file.c 5.16
SCCS-vsn: bin/csh/func.c 5.18
SCCS-vsn: bin/csh/glob.c 5.18
SCCS-vsn: bin/csh/hist.c 5.8
SCCS-vsn: bin/csh/lex.c 5.15
SCCS-vsn: bin/csh/misc.c 5.11
SCCS-vsn: bin/csh/parse.c 5.10
SCCS-vsn: bin/csh/pathnames.h 5.6
SCCS-vsn: bin/csh/proc.c 5.19
SCCS-vsn: bin/csh/sem.c 5.15
SCCS-vsn: bin/csh/set.c 5.10
SCCS-vsn: bin/csh/time.c 5.13