Make PurpleRequestFieldAccount work like a GtkCustomFilter
This makes the filtering better for introspection.
Also, fixed an incorrect type check.
Testing Done:
Enabled Demo and XMPP accounts, then tried the I'dle Mak'er plugin and confirmed that only XMPP showed in its "Set Account Idle Time" action request.
Bugs closed: PIDGIN-17780
Reviewed at https://reviews.imfreedom.org/r/2442/
# 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: