This package lacked an evolution option (to depend on
evolution-data-server). Other gnome packages had such an option,
which is highly useful to get back to a workin system in the scenario
where libffi has a new major version shlib, and evolution-data-server
won't build. Because the option defaults to on, this doesn't change
the default behavior, but those who set
PKG_DEFAULT_OPTIONS+=-evolution can be spared the build pain.
A decision about whether evolution support should be on by default or
not is pending; this change is not controversial and is being made now.
