Added missing keywords for async etc.

docs/language/dart.sty

Index: docs/language/dart.sty
===================================================================
--- docs/language/dart.sty	(revision 40975)
+++ docs/language/dart.sty	(working copy)
@@ -11,6 +11,8 @@
   \def\ABSTRACT{\builtinId{abstract}}
   \def\AS{\builtinId{as}}  
   \def\ASSERT{\keyword{assert}}
+  \def\ASYNC{\keyword{async}}
+  \def\AWAIT{\keyword{await}}
   \def\BOOLEAN{\keyword{boolean}}
   \def\BREAK{\keyword{break}}
   \def\CASE{\keyword{case}}
@@ -20,10 +22,11 @@
   \def\CONST{\keyword{const}}
   \def\CONTINUE{\keyword{continue}}
   \def\DEFAULT{\keyword{default}}
+  \def\DEFERRED{\keyword{deferred}}
   \def\DYNAMIC{\builtinId{dynamic}}
   \def\DO{\keyword{do}}
   \def\ELSE{\keyword{else}}
-    \def\ENUM{\keyword{enum}}
+  \def\ENUM{\keyword{enum}}
   \def\EQUALS{\keyword{equals}}
   \def\EXPORT{\builtinId{export}}
   \def\EXTENDS{\keyword{extends}}
@@ -60,6 +63,7 @@
   \def\STATIC{\builtinId{static}}
   \def\SUPER{\keyword{super}}  
   \def\SWITCH{\keyword{switch}}  
+  \def\SYNC{\keyword{sync}}  
   \def\THIS{\keyword{this}}
   \def\THROW{\keyword{throw}}
   \def\TRUE{\keyword{true}}
@@ -69,7 +73,8 @@
   \def\VAR{\keyword{var}}  
   \def\VOID{\keyword{void}}
   \def\WHILE{\keyword{while}}
-   \def\WITH{\keyword{with}}
+  \def\WITH{\keyword{with}}
+  \def\YIELD{\keyword{yield}}