rlm_rediswho with spaces

[Brian Candler]

OK, fixes are here:

https://github.com/candlerb/freeradius-server/commits/candlerb/redis_escaping

One commit adds escaping to rediswho_command (rlm_rediswho.c), and the other
adds de-escaping to rlm_redis_query (rlm_redis.c).

It's tested and it's working. The only question I have is, is it OK to chomp
up the string in-place in rlm_redis_query, or should I strdup it first and
free it later?

Thanks,

Brian.

P.S. I copied 'mystrtok' from valuepair.c. I checked around and there are a
couple of modules which use the standard strtok, which is not re-entrant;
is it thread-safe?