Remove unused private fields found by clang's new -Wunused-private-field.

There are some that I didn't remove this round because they looked like
obvious stubs. There are dead variables in gtest too, they should be
fixed upstream.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158090 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/RegAllocBasic.cpp

@@ -65,7 +65,6 @@ class RABasic : public MachineFunctionPass, public RegAllocBase
   MachineFunction *MF;
 
   // analyses
-  LiveStacks *LS;
   RenderMachineFunction *RMF;
 
   // state