Fixed crash at app launch on OSX 10.9 and before

The previous code crashed when run on any pre-10.9 OSX version. The reason was that the accessibility check was using a wrong function pointer to check for the new API available from 10.9. `AXIsProcessTrusted` is a function which has been available since 10.4, thus checking whether it was not null always returned true, independently of the actual system. What the original author probably wanted to check is `AXIsProcessTrustedWithOptions` which is indeed a new function introduced in 10.9.