pidgin/pidgin

Add PURPLE_VERSION and PURPLE_EXTRA_VERSION to libpurple/version.h and clean up some other related stuff
libpurple/data/purple-url-handler.desktop.in
libpurple/protocols/null/nullprpl.c
pidgin/data/im.pidgin.Pidgin.desktop.in
sub/libpurple/data/purple-url-handler.desktop.in
sub/libpurple/protocols/null/nullprpl.c
sub/pidgin/data/im.pidgin.Pidgin.desktop.in