* Migrate PurpleProtocol to the `G_DECLARE_DERIVABLE_TYPE` and `G_DEFINE_TYPE` macros.
* Rename `purple_protocol_class_*` to `purple_protocol_*`.
* Move the class properties to instance properties and add accessors as necessary.
Testing Done:
Ran locally and connected with bonjour, facebook, irc, and xmpp. Verified that the other prpls are loading and visible in the account manager.
Bugs closed: PIDGIN-17492
Reviewed at https://reviews.imfreedom.org/r/552/
# UPDATING VERSION NUMBERS FOR RELEASES
#
# The version number is:
# <major>.<minor>.<micro><extra>
#
# micro += 1
#
# If any functions have been added to libpurple, Pidgin, or Finch:
# micro = 0
# minor += 1
#
# If backwards compatibility has been broken in libpurple, Pidgin, or Finch:
# micro = 0
# minor = 0
# major += 1
# purple_soversion += 1
#
# extra should be similar to one of the following: