forked from HowardHinnant/date
Added test that detects if clock_cast<Dest>(Source) properly SFINAEs if clock's are not castable, this includes test for steady_clock that is not castable to any wall-clock. Secondly added steady_based_clock based on steady_clock (as name indicates), that clock_cast may be extended to clock non-related to wall-time (sys/utc) using conversion traits. Final example is pair of ambiguous clocks (amb1/amb2_clock) that can convert to each other either using sys_clock or utc_clock. Then the conversion from amb2 to amb1 is disambiguated via trait specialization.