Add number allocation call to runtime.cc instead of misusing

src/arm/full-codegen-arm.cc

Index: src/arm/full-codegen-arm.cc
===================================================================
--- src/arm/full-codegen-arm.cc	(revision 5036)
+++ src/arm/full-codegen-arm.cc	(working copy)
@@ -2161,12 +2161,8 @@
   __ jmp(&heapnumber_allocated);
 
   __ bind(&slow_allocate_heapnumber);
-  // To allocate a heap number, and ensure that it is not a smi, we
-  // call the runtime function FUnaryMinus on 0, returning the double
-  // -0.0. A new, distinct heap number is returned each time.
-  __ mov(r0, Operand(Smi::FromInt(0)));
-  __ push(r0);
-  __ CallRuntime(Runtime::kNumberUnaryMinus, 1);
+  // Allocate a heap number.
+  __ CallRuntime(Runtime::kNumberAlloc, 0);
   __ mov(r4, Operand(r0));
 
   __ bind(&heapnumber_allocated);