Allow keywords to be used as field names as well. This is valid by
highly discouraged

com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext

diff --git a/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext b/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext
index 63e6b96..41f1d91 100644
--- a/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext
+++ b/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext
@@ -207,7 +207,7 @@
   NormalFieldName | ExtensionFieldName;
 
 NormalFieldName:
-  target=[MessageField];
+  target=[MessageField|Name];
 
 ExtensionFieldName:
   '[' target=[MessageField|QualifiedName] ']';