Unity 5.1.2f1 Mac Fails iOS build

I'm trying to build an update to my existing Unity 5 game, which obviously needs to use IL2CPP to submit to the iOS store. On building and launching in XCode 6.4 I'm getting an error from cstring: "Semantic Issue. No member called 'memcpy' in the global namespace; did you mean 'wmemcpy'. There are 20 errors all about cstring, which is used in several Unity files generated.

I've already tried the solution setting Enable Foundation Assertions to "No" with no improvement.

In Unity's iOS Player Settings I've selected:

IL2CPP iPhone + iPad Universal Architecture Target iOS version of 6.0

Any suggestions on any XCode settings might be conflicting with the Unity build to create the error?

Regards

Andrew