[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. The memory leaks in this version have been fixed. Thanks
Alexey for pointing them out.

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

Reviewed by Andy

llvm-svn: 195064
diff --git a/llvm/lib/Support/YAMLTraits.cpp b/llvm/lib/Support/YAMLTraits.cpp
index e2108e5..42bff96f 100644
--- a/llvm/lib/Support/YAMLTraits.cpp
+++ b/llvm/lib/Support/YAMLTraits.cpp
@@ -60,6 +60,11 @@
   return EC;
 }
 
+// Pin the vtables to this file.
+void Input::HNode::anchor() {}
+void Input::EmptyHNode::anchor() {}
+void Input::ScalarHNode::anchor() {}
+
 bool Input::outputting() const {
   return false;
 }