[alarms] Fix calendar event start and end times for Qt 5.2

The workaround introduced for Qt 5.1 didn't work properly for Qt 5.2.
Remove it now.

This reverts commit cab4fbc8368b7ab496fba90e1d6d98dcc6d4fbf3.
Merge pull request #17 from pvuorela/master

[alarms] Fix calendar event start and end times for Qt 5.2