* Avoid unnecessary use of `unsigned char *`
* Use explicit casts when assigning `unsigned char *` to `char *` or vice versa
* Drop unused global variables (and fix memory leak in `gettable()`)
* Use `snprintf()` instead of `strcpy()` + `strcat()`
* Drop spurious braces in switch
Sponsored by: Klara, Inc.
Obtained from: Apple OSS Distributions (in part)
Differential Revision: https://reviews.freebsd.org/D37263
The buffer allocated in read_chat() could be 1 element too short, if the
chatstr parameter passed in is 1 or 3 charachters long (e.g. "a" or "a b").
The allocation of the pointer array does not account for the terminating
NULL pointer in that case.
Overlapping source and destination strings are undefined in strcpy().
Instead of moving a string to the left by one character just increment the
char pointer before it is assigned to the results array.
MFC after: 2 weeks
'sane' standard (not raw) settings before abort/exiting; move
responsibility of setting raw mode for chat-handling out of
chat.c to avoid doing redundant tc{s,g}etattr()s; move DE
pause prior setting standard mode before issue/login prompt to
avoid echoing modem connect strings. Fixed up comment styles
in a couple of places.
