Use do-while loops when reading start time and duration in apoint_add().
Use do-while loops when reading start time and duration in apoint_add().

Using do-while loops seems more appropriate here as "item_time" hasn't
even been read when either of the loops are entered. Spotted by
clang-analyzer.

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

lfos/calcurse,dunecn/calcurse,lfos/calcurse,lfos/calcurse,dunecn/calcurse