Change self/_cmd to be instances of ImplicitParamDecl instead of ParmVarDecl.
Patch by David Chisnall!

llvm-svn: 52422
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index 296304a..89c61ae 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -206,6 +206,7 @@
   case ObjCPropertyImpl:    nObjCPropertyImplDecl++; break;
   case LinkageSpec:         nLinkageSpecDecl++; break;
   case FileScopeAsm:        nFileScopeAsmDecl++; break;
+  case ImplicitParam:
   case TranslationUnit:     break;
 
   // FIXME: Statistics for C++ decls.