Fix end-before-start inconsistency
Fix end-before-start inconsistency

Due to deficient validation, it is possible to get an inconsistent
database with an appointment that ends before it begins. Edit an
existing one and specify an end time by a date that precedes the start
date, or create a new one and give a date as end time that precedes the
start. Then exit calcurse; on restart it will report a data error and
exit.

Signed-off-by: Lars Henriksen <a2fd37141f23d5929304549ae011a7f22ebb96a9@get2net.dk>
Signed-off-by: Lukas Fleischer <c9ca73f8336dcfb037ec2c2abf52d80a6847a5cd@calcurse.org>

lfos/calcurse,lfos/calcurse,lfos/calcurse