rename all the files (they weren't going to diff anyway)

rename all the files (they weren't going to diff anyway)
add function prototypes for extern functions, decls.h -> extern.h
delete btell function, VFORK #define, lots of other minor cleanups

SCCS-vsn: bin/csh/Makefile 5.21
SCCS-vsn: bin/csh/char.c 5.6
SCCS-vsn: bin/csh/csh.1 6.17
SCCS-vsn: bin/csh/csh.c 5.23
SCCS-vsn: bin/csh/csh.h 5.13
SCCS-vsn: bin/csh/dir.c 5.7
SCCS-vsn: bin/csh/dol.c 5.10
SCCS-vsn: bin/csh/err.c 5.7
SCCS-vsn: bin/csh/exec.c 5.13
SCCS-vsn: bin/csh/exp.c 5.8
SCCS-vsn: bin/csh/extern.h 5.2
SCCS-vsn: bin/csh/file.c 5.13
SCCS-vsn: bin/csh/func.c 5.16
SCCS-vsn: bin/csh/glob.c 5.16
SCCS-vsn: bin/csh/hist.c 5.6
SCCS-vsn: bin/csh/init.c 5.9
SCCS-vsn: bin/csh/lex.c 5.13
SCCS-vsn: bin/csh/misc.c 5.9
SCCS-vsn: bin/csh/parse.c 5.8
SCCS-vsn: bin/csh/proc.c 5.17
SCCS-vsn: bin/csh/sem.c 5.13
SCCS-vsn: bin/csh/set.c 5.7
SCCS-vsn: bin/csh/alloc.c 5.7
SCCS-vsn: bin/csh/const.c 5.2
SCCS-vsn: bin/csh/str.c 5.2
SCCS-vsn: bin/csh/time.c 5.10