Use generated Neon version of MemCopy() on ARM, if platform supports it.

src/platform-posix.cc

Index: src/platform-posix.cc
===================================================================
--- src/platform-posix.cc	(revision 14076)
+++ src/platform-posix.cc	(working copy)
@@ -315,9 +315,9 @@
 }
 
 
-#if defined(V8_TARGET_ARCH_IA32)
+#if defined(V8_GENERATED_MEMCPY)
 static OS::MemCopyFunction memcopy_function = NULL;
-// Defined in codegen-ia32.cc.
+// Defined in codegen-<arch>.cc.
 OS::MemCopyFunction CreateMemCopyFunction();
 
 // Copy memory area to disjoint memory area.
@@ -329,11 +329,11 @@
   CHECK_EQ(0, memcmp(dest, src, size));
 #endif
 }
-#endif  // V8_TARGET_ARCH_IA32
+#endif  // V8_GENERATED_MEMCPY
 
 
 void POSIXPostSetUp() {
-#if defined(V8_TARGET_ARCH_IA32)
+#if defined(V8_GENERATED_MEMCPY)
   memcopy_function = CreateMemCopyFunction();
 #endif
   init_fast_sin_function();