[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/YAMLParser.cpp b/llvm/lib/Support/YAMLParser.cpp
index 9e50612..9495cd4 100644
--- a/llvm/lib/Support/YAMLParser.cpp
+++ b/llvm/lib/Support/YAMLParser.cpp
@@ -96,6 +96,15 @@
 
 namespace llvm {
 namespace yaml {
+/// Pin the vtables to this file.
+void Node::anchor() {}
+void NullNode::anchor() {}
+void ScalarNode::anchor() {}
+void KeyValueNode::anchor() {}
+void MappingNode::anchor() {}
+void SequenceNode::anchor() {}
+void AliasNode::anchor() {}
+
 /// Token - A single YAML token.
 struct Token : ilist_node<Token> {
   enum TokenKind {