Added builtin native call to exit the running vm

runtime/bin/builtin.dart

Index: runtime/bin/builtin.dart
diff --git a/runtime/bin/builtin.dart b/runtime/bin/builtin.dart
index c54c48619e6e1e85bbf3fc9a01e75f49887b8911..9fa761098dd02c20403fcbc427d5ba529a63e2fa 100644
--- a/runtime/bin/builtin.dart
+++ b/runtime/bin/builtin.dart
@@ -8,6 +8,14 @@ void print(arg) {
   _Logger._printString(arg.toString());
 }
 
+void exit(int status) {
+  _Runtime._exit(status);

[Ivan Posva, 2011/10/19 21:57:11]

If called like this:
exit("0");
The VM will run into an assertion, instead you should check that only arguments
with the correct type are forwarded into native code:

void exit(int status) {
  if (status is !int) {
    throw IllegalArgumentException("int status expected");
  }
  _exit(status);
}

_exit(int status) native "_exit";

[rchandia, 2011/10/21 17:29:41]

Done.

+}
+
 class _Logger {
   static void _printString(String s) native "Logger_PrintString";
 }
+
+class _Runtime {

[Ivan Posva, 2011/10/19 21:57:11]

There is no need to add a class as a wrapper here. A top-level native function
_exit would be good enough. Eventually we should do the same thing for Logger,
which only exists due to legacy (all of the Logger functionality has been
gutted.)

[rchandia, 2011/10/21 17:29:41]

Done.

+  static void _exit(int status) native "Runtime_Exit";
+}