[weak vtables] Remove a bunch of weak vtables

This patch removes most of the trivial cases of weak vtables by pinning them to
a single object file.

Differential Revision: http://llvm-reviews.chandlerc.com/D2068

Reviewed by Andy

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194865 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/IR/Value.cpp b/lib/IR/Value.cpp
index 35808a6..a56272f 100644
--- a/lib/IR/Value.cpp
+++ b/lib/IR/Value.cpp
@@ -735,9 +735,5 @@
 #endif
 }
 
-// Default implementation for CallbackVH.
-void CallbackVH::allUsesReplacedWith(Value *) {}
-
-void CallbackVH::deleted() {
-  setValPtr(NULL);
-}
+// pin vtable to this file
+void CallbackVH::anchor() {}