Disregard milliseconds in QTime::secsTo().

Disregard milliseconds in QTime::secsTo().

"The documentation states that "secsTo() does not take into account any
milliseconds", however, this is not the case. Given times 12:30:01.500
and 12:30:02.400 secsTo returns 0. If milliseconds are not taken into
account, I would expect this to return 1 (i.e. interprets the times as
12:30:01 and 12:30:02 thus truncating the milliseconds)."

Note that tests were also written for QDateTime::secsTo(), as it uses
QTime::secsTo internally. This addresses Javier's issue in the
comments of QTBUG-9304.

Task-number: QTBUG-9304
Change-Id: I9efe0c8f710db859c1d086d67ba3e5b349a56c4e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>