Second round of cleanups for new optional parameter semantics.

utils/template/world.dart

Index: utils/template/world.dart
===================================================================
--- utils/template/world.dart	(revision 13754)
+++ utils/template/world.dart	(working copy)
@@ -126,7 +126,7 @@
 
   /** [message] at [location] is so bad we can't generate runnable code. */
   void fatal(String message,
-      [SourceSpan span, SourceSpan span1, SourceSpan span2]) {
+      {SourceSpan span, SourceSpan span1, SourceSpan span2}) {
     errors++;
     seenFatal = true;
     _message(_RED_COLOR, 'fatal: ', message,
@@ -135,7 +135,7 @@
 
   /** [message] at [location] is about a bug in the compiler. */
   void internalError(String message,
-      [SourceSpan span, SourceSpan span1, SourceSpan span2]) {
+      {SourceSpan span, SourceSpan span1, SourceSpan span2}) {
     _message(_NO_COLOR,
         'We are sorry, but...', message, span, span1, span2, true);
   }