Add the CoreFoundation and IOKit framework linker flags on MacOS X
when configuring for USB support.
patch #4685: Libusb on MacOS X: detection and additional includes
Thanks to Matthias Ringwald for testing the reworked patch.
git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk@666 81a1dc3b-b13d-400b-aceb-764788c761c2