Move some flag-like props from GlobalContext and TargetLowering to ClFlags.

src/IceTargetLoweringX8632.h

Index: src/IceTargetLoweringX8632.h
diff --git a/src/IceTargetLoweringX8632.h b/src/IceTargetLoweringX8632.h
index aa160104b7d86ffbb35bec785b466ea865ebe260..74e0d503588b90e318e0bd6b37363ab3479121e8 100644
--- a/src/IceTargetLoweringX8632.h
+++ b/src/IceTargetLoweringX8632.h
@@ -71,9 +71,11 @@ public:
   x86::Address stackVarToAsmOperand(const Variable *Var) const;
 
   enum X86InstructionSet {
+    Begin,
     // SSE2 is the PNaCl baseline instruction set.
-    SSE2,
-    SSE4_1
+    SSE2 = Begin,
+    SSE4_1,
+    End
   };
 
   X86InstructionSet getInstructionSet() const { return InstructionSet; }