[nem-en] Bugs in extension method implementation

[vc]

   > It wasn't as hard as it seemed. Fixed :-)
   
   If extension method contains in external assembly it's don't work.
   For example see 
 
http://nemerle.org/svn/vs-plugin/trunk/Nemerle.Compiler.Utils/Nemerle.Comple
tion2/CodeModel/Project.MakeCompletionList.n
   
   line 30:
   
   def addMember(member : IMember)
   {
     when (IsValid(member))
       //Fixme: member.GetName() don't compile.
       add (Completion.GetName(member), Elem.Member(member))
   } 
   
   The GetName() implementation contain in
http://nemerle.org/svn/nemerle/trunk/ncc/completion/CodeCompletionEngine.n