DDASLLogCapture fixed for Xcode 6 running on iOS7 simulator in OS X Yosemite

i was still running into the issue with `asl_(next|release)` vs `aslresponse_(next|release)` in my environment
i fixed it using the idea rodmaz mentioned [here](https://github.com/CocoaLumberjack/CocoaLumberjack/issues/333), and using function pointers to make the code cleaner and more readable