Minor speedups & cleanups:

Minor speedups & cleanups:
replace letter() et al with ctype-like cmap macros and expand cmap to short
for new LET and DIG bits; use bzero in private calloc; make btell a macro.

SCCS-vsn: bin/csh/csh.h 5.3
SCCS-vsn: bin/csh/char.h 5.3
SCCS-vsn: bin/csh/char.c 5.3
SCCS-vsn: bin/csh/misc.c 5.3
SCCS-vsn: bin/csh/dol.c 5.3
SCCS-vsn: bin/csh/lex.c 5.4