pidgin/pidgin

Install our appdata file to $(datadir)/metainfo as that change was made a long time ago

This patch originates from Lars Wendler from Gentoo

https://gitweb.gentoo.org/repo/gentoo.git/commit/net-im/pidgin/files/pidgin-2.13.0-metainfo.patch?id=2dd6c1852251b5b67c3045badf173be9535b97a9

Testing Done:
Installed to a prefix and verified the file ended up in `$prefix/share/metainfo`

Reviewed at https://reviews.imfreedom.org/r/607/
/** @page plugin-signals Plugin Signals
@signals
@signal plugin-load
@signal plugin-unload
@endsignals
@see plugin.h
<hr>
@signaldef plugin-load
@signalproto
void (*plugin_load)(PurplePlugin *plugin);
@endsignalproto
@signaldesc
Emitted when a plugin is loaded.
@param plugin The plugin that was loaded.
@endsignaldef
@signaldef plugin-unload
@signalproto
void (*plugin_unload)(PurplePlugin *plugin);
@endsignalproto
@signaldesc
Emitted when a plugin is unloaded.
@param plugin The plugin that was unloaded.
@endsignaldef
*/
// vim: syntax=c.doxygen tw=75 et