Revert r194865 and r194874.

This change is incorrect. If you delete virtual destructor of both a base class
and a subclass, then the following code:
  Base *foo = new Child();
  delete foo;
will not cause the destructor for members of Child class. As a result, I observe
plently of memory leaks. Notable examples I investigated are:
ObjectBuffer and ObjectBufferStream, AttributeImpl and StringSAttributeImpl.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194997 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ExecutionEngine/ObjectCache.h

@@ -20,7 +20,6 @@ class Module;
 /// ExecutionEngine for the purpose of avoiding compilation for Modules that
 /// have already been compiled and an object file is available.
 class ObjectCache {
-  virtual void anchor();
 public:
   ObjectCache() { }