Make two vtable tests tolerate C++11

[probinson]

Summary

In C++11, we don't emit vtables as eagerly as we do for C++03, so fiddle the tests to emit them when the test expects them.

In the C++11 test cleanup project, we're commonly making the tests run in both dialects and sometimes with no dialect specified (as Clang's default will presumably advance to C++14/17 at some point). I didn't do that for vtable-layout.cpp because it runs FileCheck 46 times, and replicating that really seemed like too much.
If it also seems like too much for vtable-linkage.cpp, the easy thing is to force it to C++03.

[rjmccall]

No, seems fine to me.

test/CodeGenCXX/vtable-layout.cpp

struct C: public B {
     virtual int f();
     virtual int g(int);
     virtual int g();
     virtual int h(int);
     virtual int h();
     virtual int i(int);
     virtual int i();
   };
+  // Force C's vtable to be generated.
+  int C::f() { return 1; }
 
   class D : C {};
 
   D d;
 }

test/CodeGenCXX/vtable-linkage.cpp

 // RUN: %clang_cc1 %s -triple=x86_64-pc-linux -emit-llvm -o %t
+// RUN: %clang_cc1 %s -triple=x86_64-pc-linux -emit-llvm -std=c++03 -o %t.03
+// RUN: %clang_cc1 %s -triple=x86_64-pc-linux -emit-llvm -std=c++11 -o %t.11
 // RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -disable-llvm-optzns -O3 -emit-llvm -o %t.opt
 // RUN: FileCheck %s < %t
+// RUN: FileCheck %s < %t.03
+// RUN: FileCheck %s < %t.11
 // RUN: FileCheck --check-prefix=CHECK-OPT %s < %t.opt
 
 namespace {
   struct A {
     virtual void f() { }
   };
 }
 

 struct D {
   virtual void f();
 };
 
 void D::f() { }
 
 static struct : D { } e;
 
+// Force 'e' to be constructed and therefore have a vtable defined.
+void use_e() {
+  e.f();
+}
+
 // The destructor is the key function.
 template<typename T>
 struct E {
   virtual ~E();
 };
 
 template<typename T> E<T>::~E() { }