Error out if filter expression is attached to unsupported event types

Attaching a filter on a probe event, a function event or an
userspace-probe event is not supported by the LTTng kernel tracer. So we
do an early sanity check in the lttng-enable-event and warn the user if
the filtering is not supported.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>