In progress: [Issue 29] Problems with "extend"
https://code.google.com/p/protobuf-dt/issues/detail?id=29

Added initial work in the grammar.

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 5b36a68..7e8fbc7 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
@@ -126,7 +126,7 @@
   name=ID '=' index=INT ';';
 
 ExtendMessage:
-  'extend' message=[Message] '{'
+  'extend' message=MessageReference '{'
   elements+=MessageElement*
   '}';