- Implement a first cut for const String.env in the VM to allow

sdk/lib/core/int.dart

Index: sdk/lib/core/int.dart
===================================================================
--- sdk/lib/core/int.dart	(revision 27984)
+++ sdk/lib/core/int.dart	(working copy)
@@ -252,4 +252,11 @@
   external static int parse(String source,
                             { int radix,
                               int onError(String source) });
+
+  /**

[bakster, 2013/09/27 07:44:39]

Too long lines.

[Ivan Posva, 2013/09/27 21:05:06]

Thanks for noticing. Comments will need to be updated to match the naming in any
case.

+   * Returns the integer value for the given environment variable [name] or [defaultValue]
+   * if [name] is not present. If the value of the environment variable is not a valid
+   * integer literal a [FormatException] is thrown.

[Lasse Reichstein Nielsen, 2013/09/28 00:13:38]

Consider reformatting as:

  The integer value of the environment value for the key `name`.
  
  If [name] is not an environment key, instead returns [defaultValue].

  Throws a [FormatException] if the environment value is not an
  integer literal.

I try to avoid "returns" since it is a constructor, but that is what it does
with [defaultValue]. That suggests that it is an odd kind of constructor - more
like a factory constructor. Maybe mark it as such, if it has to be a constructor
at all. 

+   */
+  external int.env(String name, int defaultValue);

[Lasse Reichstein Nielsen, 2013/09/28 00:13:38]

Why is this a constructor instead of a static function?

I seem to remember the idea was to make it a const constructor (so the  value
would be a const value), but in that case, it can't throw.

 }