Fix finding locale from OS on Windows

pkg/intl/intl.dart

Index: pkg/intl/intl.dart
===================================================================
--- pkg/intl/intl.dart	(revision 12463)
+++ pkg/intl/intl.dart	(working copy)
@@ -141,10 +141,13 @@
     // Locales of length < 5 are presumably two-letter forms, or else malformed.
     // Locales of length > 6 are likely to be malformed. In either case we
     // return them unmodified and if correct they will be found.
+    // We treat C as a special case, and assume it wants en_ISO for formatting.
+    if (aLocale == "C") return "en_ISO";

[Emily Fortuna, 2012/09/18 00:46:33]

what does "C" mean?

[Alan Knight, 2012/09/18 17:08:36]

It's an old Unix locale, also referred to as the Posix locale. It uses 7-bit
ascii, and some basic date formatting conventions. You don't see it a whole lot
on a real system nowadays, but you do get it as the locale on Cygwin, so I
thought it was worth compensating for it, and at least making sure it got
English conventions. The en_ISO is probably not quite right for date and number
formats, but I don't think we're likely to see it for end users, so it's
probably ok if we're close enough. But I put in a TODO to validate it and
consider including real data for it.

[Emily Fortuna, 2012/09/18 17:38:09]

Can you maybe mention a little bit of that in your comment above? (ignore if
this is common knowledge)

     if ((aLocale.length < 5) || (aLocale.length > 6)) return aLocale;
     if (aLocale[2] != '-' && (aLocale[2] != '_')) return aLocale;
+    var lastRegionLetter = aLocale.length == 5 ? "" : aLocale[5].toUpperCase();
     return '${aLocale[0]}${aLocale[1]}_${aLocale[3].toUpperCase()}'
-           '${aLocale[4].toUpperCase()}';
+           '${aLocale[4].toUpperCase()}$lastRegionLetter';
   }
 
   /**