Revert r211399, "Generate native unwind info on Win64"

It broke Legacy JIT Tests on x86_64-{mingw32|msvc}, aka Windows x64.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211480 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetFrameLowering.h

@@ -93,19 +93,6 @@ public:
   /// stack pointer.
   virtual bool isFPCloseToIncomingSP() const { return true; }
 
-  /// assignCalleeSavedSpillSlots - Allows target to override spill slot
-  /// assignment logic.  If implemented, assignCalleeSavedSpillSlots() should
-  /// assign frame slots to all CSI entries and return true.  If this method
-  /// returns false, spill slots will be assigned using generic implementation.
-  /// assignCalleeSavedSpillSlots() may add, delete or rearrange elements of
-  /// CSI.
-  virtual bool
-  assignCalleeSavedSpillSlots(MachineFunction &MF,
-                              const TargetRegisterInfo *TRI,
-                              std::vector<CalleeSavedInfo> &CSI) const {
-    return false;
-  }
-
   /// getCalleeSavedSpillSlots - This method returns a pointer to an array of
   /// pairs, that contains an entry for each callee saved register that must be
   /// spilled to a particular stack location if it is spilled.