Issue# 13313: Add Line Islands Standard Time

Okay. I updated the windows time zone name conversions per http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/zone_tzid.html and then added Line Islands Standard Time from http://support.microsoft.com/kb/2981580 (it has yet to be added to the first link).

In addition to that I put the script that I used to regenerate the time zone name conversions at the bottom of std.datetime so that it will be easier to make such updates in the future.

I also changed `tzDatabaseNameToWindowsTZName` and `windowsTZNameToTZDatabaseName` so that they return `null` on failure rather than throwing as explained here:

https://issues.dlang.org/show_bug.cgi?id=13319