Add "sub immediate" instruction to the ARM integrated assembler.

src/IceAssemblerARM32.h

Index: src/IceAssemblerARM32.h
diff --git a/src/IceAssemblerARM32.h b/src/IceAssemblerARM32.h
index 839b30e0dafd2a6755fff7d8f30946ca6951c9d7..d4e2c0ac7987d45e6ba1142b8b334563fc832a82 100644
--- a/src/IceAssemblerARM32.h
+++ b/src/IceAssemblerARM32.h
@@ -107,6 +107,9 @@ public:
 
   void bx(RegARM32::GPRRegister Rm, CondARM32::Cond Cond = CondARM32::AL);
 
+  void sub(const Operand *OpRd, const Operand *OpRn, const Operand *OpSrc1,
+           bool SetFlags, CondARM32::Cond Cond);
+
   static bool classof(const Assembler *Asm) {
     return Asm->getKind() == Asm_ARM32;
   }