* Change some functions to use `ZSubscription_t`
* Cleanup redundant `zephyr_triple` allocations
* Inline `zephyr_subscribe_failed`
* Replace `find_sub_by_sub` and `find_sub_by_id` with `g_slist_find_custom`
* Rename functions related to `zephyr_triple`
Testing Done:
Compile.
Reviewed at https://reviews.imfreedom.org/r/450/
# 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: