Note in protocol-dbus.c specifically, method_signatures needs to be freed
before method_handlers, because otherwise h->method_name is freed while it is
still in use as a key in the method_signatures hashmap.
There were several memory leaks. In addition to those,
pa_dbus_protocol_add_interface() used a string from the
caller as a key to a hashmap, instead of a copy of the
string. This caused trouble when the caller freed the
string while the key was still in use in the hashmap.
We should not call pa_core_ref() anywhere in the code. Doing so
will prevent proper daemon shutdown as the only call (in daemon/main.c)
to pa_core_unref() should always call free_core() and perform a normal
shutdown (i.e. unload all modules gracefully).
Previously we used libdbus's memory as keys in listening_signals, which caused
that the memory of the hashmap keys got overwritten, which led to that signals
weren't sent properly.
