Implement querying the current absolute time on Windows which was
previously marked as unimplemented. Use the
`GetSystemTimePreciseAsFileTime` to query the system time which is in
100-ns intervals since January 1, 1601 (UTC). This partially enables
the `Date` functionality on Windows.
MSVCRT does not provide `gmtime_r`. `gmtime` is re-entrant safe, but
uses TLS storage. Prefer to use `_gmtime64_s` which provides the
re-entrancy with local buffers but swaps parameter orders. Prefer to
use the 64-bit time variant over the 32-bit `time_t`.
* Fixes issue #78: Calling Date.description might result in undefined behaviour
The buffer used was too small in some cases.
Fixed by allocating (more than) enough space on the stack.
* Fixed indentation.
* Removed explicit return type.
* Added tests and added workarounds for glibc non-standard behaviour.
Also limited description to show dates in the range .distantPast to
.distandFuture since values way outside that range sometimes result in
incorrect results.
