Add various forms of LDREX/STREX to ARM integrated assembler.

src/DartARM32/assembler_arm.cc

Index: src/DartARM32/assembler_arm.cc
diff --git a/src/DartARM32/assembler_arm.cc b/src/DartARM32/assembler_arm.cc
index e7295e7ea557afa4a62c3a7eb1787535af133c2a..b6d27126b33f3ff8b1a74116ea771dd083feba1e 100644
--- a/src/DartARM32/assembler_arm.cc
+++ b/src/DartARM32/assembler_arm.cc
@@ -557,9 +557,8 @@ void Assembler::stm(BlockAddressMode am, Register base, RegList regs,
   ASSERT(regs != 0);
   EmitMultiMemOp(cond, am, false, base, regs);
 }
-#endif
-
 
+// Moved to ARM::AssemblerARM32::ldrex();
 void Assembler::ldrex(Register rt, Register rn, Condition cond) {
   ASSERT(TargetCPUFeatures::arm_version() != ARMv5TE);
   ASSERT(rn != kNoRegister);
@@ -575,7 +574,7 @@ void Assembler::ldrex(Register rt, Register rn, Condition cond) {
   Emit(encoding);
 }
 
-
+// Moved to ARM::AssemblerARM32::strex();
 void Assembler::strex(Register rd, Register rt, Register rn, Condition cond) {
   ASSERT(TargetCPUFeatures::arm_version() != ARMv5TE);
   ASSERT(rn != kNoRegister);
@@ -591,7 +590,7 @@ void Assembler::strex(Register rd, Register rt, Register rn, Condition cond) {
                      (static_cast<int32_t>(rt) << kStrExRtShift);
   Emit(encoding);
 }
-
+#endif
 
 void Assembler::clrex() {
   ASSERT(TargetCPUFeatures::arm_version() != ARMv5TE);