Introduce the notion of function addresses in Subzero.

src/IceTargetLowering.h

Index: src/IceTargetLowering.h
diff --git a/src/IceTargetLowering.h b/src/IceTargetLowering.h
index f116cf31ea685546402ea759fee5172e29822570..bbda1f8b0b36fa8e1a62131282cd0d63877bb942 100644
--- a/src/IceTargetLowering.h
+++ b/src/IceTargetLowering.h
@@ -27,7 +27,6 @@ namespace Ice {
 typedef uint8_t AsmCodeByte;
 
 class Assembler;
-class GlobalAddress;
 
 // LoweringContext makes it easy to iterate through non-deleted
 // instructions in a node, and insert new (lowered) instructions at
@@ -249,7 +248,7 @@ public:
                                                   GlobalContext *Ctx);
   virtual ~TargetGlobalInitLowering();
 
-  virtual void lower(const GlobalAddress &Addr, bool DisableTranslation) = 0;
+  virtual void lower(const VariableDeclaration &Var) = 0;
 
 protected:
   TargetGlobalInitLowering(GlobalContext *Ctx) : Ctx(Ctx) {}