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

lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.cpp

@@ -37,9 +37,6 @@
 
 using namespace llvm;
 
-// pin vtable to this file
-PPCTargetStreamer::~PPCTargetStreamer() {}
-
 static MCInstrInfo *createPPCMCInstrInfo() {
   MCInstrInfo *X = new MCInstrInfo();
   InitPPCMCInstrInfo(X);