Make splitter connect to signals with PURPLE_SIGNAL_PRIORITY_LOWEST, which
should cause it to be called before other plugins, such as OTR. I believe
this fixes #571.
#
# pidgin_major_ver and pidgin_minor_ver should be defined to match the minimum
# Pidgin API version _required_ to build Plugin Pack
# Due to the way Pidgin checks plugin versions, we need to also ensure that
# the correct minimum version of Pidgin is Require:'d based on what version of