Add initial integrated assembler w/ some Xmm ops.

src/IceTargetLowering.h

Index: src/IceTargetLowering.h
diff --git a/src/IceTargetLowering.h b/src/IceTargetLowering.h
index 99716be9981272f092c4c9648fa599d4811c1f1b..37e14dfd9361596d4ea092c56c0110169636d7ce 100644
--- a/src/IceTargetLowering.h
+++ b/src/IceTargetLowering.h
@@ -25,6 +25,8 @@
 
 namespace Ice {
 
+class Assembler;
+
 // LoweringContext makes it easy to iterate through non-deleted
 // instructions in a node, and insert new (lowered) instructions at
 // the current point.  Along with the instruction list container and
@@ -87,6 +89,7 @@ private:
 class TargetLowering {
 public:
   static TargetLowering *createLowering(TargetArch Target, Cfg *Func);
+  static Assembler *createAssembler(TargetArch Target, Cfg *Func);
   void translate() {
     switch (Ctx->getOptLevel()) {
     case Opt_m1: