migrate raw string to new syntax in pkg

pkg/intl/lib/intl_standalone.dart

Index: pkg/intl/lib/intl_standalone.dart
===================================================================
--- pkg/intl/lib/intl_standalone.dart	(revision 12745)
+++ pkg/intl/lib/intl_standalone.dart	(working copy)
@@ -51,7 +51,7 @@
  * Regular expression to match the expected output of systeminfo on
  * Windows. e.g. System Locale:<tab>en_US;English (United States)
  */
-RegExp _sysInfoRegex = const RegExp(@"System Locale:\s+(\w\w-\w+);");
+RegExp _sysInfoRegex = const RegExp(r"System Locale:\s+(\w\w-\w+);");
 
 /**
  * Regular expression to match the expected output of reading the defaults
@@ -61,7 +61,7 @@
  *     "pt-PT",
  *     ...
  */
-RegExp _appleDefaultsRegex = const RegExp(@'(\w\w_\w+)');
+RegExp _appleDefaultsRegex = const RegExp(r'(\w\w_\w+)');
 
 /**
  * Check to see if we have a "LANG" environment variable we can use and return