pidgin/pidgin

Add config.h in another header that needs it.

2020-07-27, Elliott S
81417b812648
Add config.h in another header that needs it.

Actually, some irc C files check `HAVE_CYRUS_SASL` too, and probably
were not compiling with it since they don't seem to include the config
either.

Testing Done:
Compile only

Reviewed at https://reviews.imfreedom.org/r/52/
[Desktop Entry]
Name=Pidgin
GenericName=Internet Messenger
Comment=Chat over IM. Supports AIM, Google Talk, Jabber/XMPP, and more
Exec=purple3-url-handler %u
TryExec=purple3-url-handler
Icon=pidgin
StartupNotify=false
Terminal=false
NoDisplay=true
Type=Application
Categories=Network;InstantMessaging;RemoteAccess;ConsoleOnly;
MimeType=x-scheme-handler/aim;x-scheme-handler/gg;x-scheme-handler/icq;x-scheme-handler/irc;x-scheme-handler/msnim;x-scheme-handler/sip;x-scheme-handler/xmpp;x-scheme-handler/ymsgr
@USES_MM_CHAT_SECTION@