now connid's are allocated on demand and clients may have as many connid's as necessary.
this allows us to build chains of helpers while ensuring the ircd properly tracks and GCs the resources.
Charybdis requires C99 already, so it's high time we start using
stdbool. I've converted a few pieces of code already.
A lot of the old code that uses YES/NO should probably be updated too
because that's fucking hideous.
It's possible for which_ssld to fail and return NULL, handle this in
start_ssld_connect and start_ssld_accept by returning NULL. The NULL
return value is already handled in all calls to start_ssld_accept,
so handle this for start_ssld_connect by reporting an error connecting.
Handle it in start_zlib_session by exiting the client.
