Unweaken vtables as per http://llvm.org/docs/CodingStandards.html#ll_virtual_anch

llvm-svn: 146959
diff --git a/clang/lib/Analysis/ReachableCode.cpp b/clang/lib/Analysis/ReachableCode.cpp
index 62575f9..bb63e2c 100644
--- a/clang/lib/Analysis/ReachableCode.cpp
+++ b/clang/lib/Analysis/ReachableCode.cpp
@@ -251,7 +251,9 @@
 }
 
 namespace clang { namespace reachable_code {
-  
+
+void Callback::anchor() { }  
+
 unsigned ScanReachableFromBlock(const CFGBlock *Start,
                                 llvm::BitVector &Reachable) {
   unsigned count = 0;