Add DMB instruction to the ARM integrated assembler.

src/IceAssemblerARM32.h

Index: src/IceAssemblerARM32.h
diff --git a/src/IceAssemblerARM32.h b/src/IceAssemblerARM32.h
index 63a82d550f6b3cbbdeaaeeac6a7a549c6c76f4f0..cf95eb1e97b4e8a7b7f4ef7aa8de4a843f1a60f5 100644
--- a/src/IceAssemblerARM32.h
+++ b/src/IceAssemblerARM32.h
@@ -209,6 +209,8 @@ public:
 
   void cmp(const Operand *OpRn, const Operand *OpSrc1, CondARM32::Cond Cond);
 
+  void dmb(IValueT Option); // Option is a 4-bit value.
+
   void eor(const Operand *OpRd, const Operand *OpRn, const Operand *OpSrc1,
            bool SetFlags, CondARM32::Cond Cond);