Fixes for Mac OS X and parallel compilation

I think the issue you encountered on OS X could happen on any platform with parallel compilation - I added aes.a to LDFLAGS, and I only marked the john executable as requiring the AES folder to actually be built, so I suspect it was one of the other executables being linked that threw the error for you. Simple fix - move aes.a from LDFLAGS to the line specific for building the john executable.

That said, I don't have access to an OS X machine with more than two processor cores, and I couldn’t replicate that particular issue. So if you could double check if these changes help on a machine that can actually run eight things in parallel, it'd be appreciated.

Also, while building on a Mac OS X Mavericks machine, I discovered a small problem that could occur while building part of the wrapper, so that's been fixed.