Only werase() calendar if month is changed
Only werase() calendar if month is changed

Optimize the monthly view by only erasing the window content when a new
month is selected.

Signed-off-by: Lukas Fleischer <af90e31281d8305af43dc616c5aaca3c7165f8a7@cryptocrack.de>

lfos/calcurse,lfos/calcurse,lfos/calcurse