cleanup: move minute formating to format-string.cpp

The get_minutes() function formats a time as m:ss
and returns a static C-string. Since all callers are
C++ anyway and transform directly into QString, let us
move this to the other string formatting function.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/string-format.cpp

@@ -277,6 +277,11 @@ QString formatDayOfWeek(int day)
 	}
 }
 
+QString formatMinutes(int seconds)
+{
+	return QString::asprintf("%d:%.2d", FRACTION(seconds, 60));
+}
+
 QString formatTripTitle(const dive_trip *trip)
 {
 	if (!trip)