It was possible to select the cell after the last day of the month by
clicking on it.
The days variable is the first day of the month cell + the number of
days in the month, so only cells less than this cell should be
considered actual month days.
https://bugzilla.gnome.org/show_bug.cgi?id=763495
tzid can have different formats depending on where it originates from:
regular or prefixed by a libical specific identifier. Use the
right icaltimezone_get_builtin_timezone* for each case.
https://bugzilla.gnome.org/show_bug.cgi?id=763180
format_utc_offset can be called with the return value of
g_date_time_get_utc_offset returning microseconds in a gint64. It is
also still called with the return value of icaltimezone_get_utc_offset
in seconds. Deal with both.
https://bugzilla.gnome.org/show_bug.cgi?id=762438
fosero