pidgin/pidgin

Make sure all of the final types in pidgin plugins are defined as such

Testing Done:
Loaded both plugins and verified their dialogs still worked.

Reviewed at https://reviews.imfreedom.org/r/2923/
PURPLE_HISTORY_SOURCES = [
'purplehistorycore.c',
]
executable('purple-history',
PURPLE_HISTORY_SOURCES,
dependencies : [libpurple_dep, glib],
install : true)