Fixed a crash in Clang when a superclass of an

Objective-C class doesn't have a definition but
Clang tries to read through its protocols anyway.

llvm-svn: 154538

lldb/scripts/clang.check-definition-for-superclasses.diff

@@ -0,0 +1,15 @@
+Index: lib/AST/DeclObjC.cpp
+===================================================================
+--- lib/AST/DeclObjC.cpp	(revision 152265)
++++ lib/AST/DeclObjC.cpp	(working copy)
+@@ -330,6 +330,10 @@
+     LoadExternalDefinition();
+ 
+   while (ClassDecl != NULL) {
++    // FIXME: Should make sure no callers ever do this.
++    if (!ClassDecl->hasDefinition())
++      return 0;
++        
+     if ((MethodDecl = ClassDecl->getMethod(Sel, isInstance)))
+       return MethodDecl;
+