[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

examples/Kaleidoscope/Chapter4/toy.cpp

@@ -91,10 +91,12 @@ static int gettok() {
 /// ExprAST - Base class for all expression nodes.
 class ExprAST {
 public:
-  virtual ~ExprAST() {}
+  virtual ~ExprAST();
   virtual Value *Codegen() = 0;
 };
 
+ExprAST::~ExprAST() {}
+
 /// NumberExprAST - Expression class for numeric literals like "1.0".
 class NumberExprAST : public ExprAST {
   double Val;