pidgin/pidgin

Use GPLUGIN_NATIVE_PLUGIN_DECLARE for all libpurple plugins and remove PURPLE_PLUGIN_INIT

Testing Done:
Ran an instance and verified my enabled accounts connected and everything else was queried successfully.

Reviewed at https://reviews.imfreedom.org/r/741/
nullclient = executable('nullclient', 'nullclient.c', 'defines.h',
c_args : ['-DSTANDALONE'],
dependencies : [libpurple_dep, glib])