Fix notification of recurrent appointments
Fix notification of recurrent appointments

The recur_apoint_starts_before() filter function expected the second
parameter to be passed by value, whereas its only caller passed the
value by reference. For consistency with apoint_starts_after(), change
the signature and the implementation of recur_apoint_starts_before()
such that the parameter is passed by reference.

Also, add a comment to the only caller of recur_apoint_starts_before()
to clarify on why recur_apoint_starts_before() is used.

Fixes GitHub issue #25.

Signed-off-by: Lukas Fleischer <c9ca73f8336dcfb037ec2c2abf52d80a6847a5cd@calcurse.org>

lfos/calcurse,lfos/calcurse,lfos/calcurse