Add Mode64Bit feature and sink it down to MC layer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134641 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86TargetMachine.cpp b/lib/Target/X86/X86TargetMachine.cpp
index 1b6fa30..aaf15fd 100644
--- a/lib/Target/X86/X86TargetMachine.cpp
+++ b/lib/Target/X86/X86TargetMachine.cpp
@@ -120,7 +120,7 @@
                                    const std::string &CPU,
                                    const std::string &FS, bool is64Bit)
   : LLVMTargetMachine(T, TT),
-    Subtarget(TT, CPU, FS, is64Bit, StackAlignmentOverride),
+    Subtarget(TT, CPU, FS, StackAlignmentOverride),
     FrameLowering(*this, Subtarget),
     ELFWriterInfo(is64Bit, true) {
   DefRelocModel = getRelocationModel();