Create file to test util functions and create a test for the
gcal_date_time_from_icaltime function. The test checks if the time
zones are correctly interpreted in the conversion of an ICalTime to a
GDateTime.
Getting the time zone based on the location of the event doesn't work
with virtual time zones, causing the offset to be incorrect on the
import dialog. This changes the function to adjust the time zone of the
GDateTime based on the offset from UTC, which should work for both
virtual and real timezones.
See #1243
When dealing with floating time events the timezone used was UTC,
but according to RFC5545 when the timezone is not specified the
local timezone should be used.
Fixes#171
Felipe Anibal