pidgin/pidgin

Use G_DECLARE_DERIVABLE_TYPE for PurpleConversation and additional cleanups

The setters for PurpleConversation are kind of crappy because of the
conversation cache in the purple_conversations api, which we'll address at a
later time.

Testing Done:
Compiled and ran locally, parted a chat and just signed out to verify no new issues.

Reviewed at https://reviews.imfreedom.org/r/613/
#ifndef PURPLE_ZEPHYR_INTERNAL_H
#define PURPLE_ZEPHYR_INTERNAL_H
#include <sysdep.h>
#ifdef LIBZEPHYR_EXT
#include <zephyr/zephyr.h>
#else
#include <zephyr_internal.h>
#endif
#ifdef WIN32
#ifndef MAXHOSTNAMELEN
#define MAXHOSTNAMELEN 512
#endif
#define ETIMEDOUT WSAETIMEDOUT
#define EADDRINUSE WSAEADDRINUSE
#else /* !WIN32 */
#include <netdb.h>
#ifndef MAXHOSTNAMELEN
#define MAXHOSTNAMELEN 4096
#endif
#endif
#ifdef ZEPHYR_USES_HESIOD
#include <hesiod.h>
#endif
#ifndef ZEPHYR_USES_KERBEROS
#define REALM_SZ MAXHOSTNAMELEN
#define INST_SZ 0 /* no instances w/o Kerberos */
#define ANAME_SZ 9 /* size of a username + null */
#define CLOCK_SKEW 300 /* max time to cache packet ids */
#endif
#endif /* PURPLE_ZEPHYR_INTERNAL_H */