unbreak. remove yk_ndef_st name and map both YKNDEF and YK_NDEF to ndef_st
NEWS for next release
extern on function yk_write_ndef()
mention yk_challenge_response()
make yk_challenge_response() take challenge as const
when calling libusb_exit() clear usb_ctx and libusb_inited
correct indentation
fix NEWS about ndef_construct return values
bump version to 1.8.0 for release
bump versions post-release
IOHIDManager object have to be disposed of with CFRelease()
remove extra spaces in ykcore_osx
make error handling match that of other ykcore implementations
ignore more ykcore backends
don't do IOHIDManagerClose() in stop

it's used for matching IOHIDManagerOpen() not IOHIDManagerCreate()
we need to CFRetain(yk) after opening the device

and do CFRelease() when closing the device
don't do yk_release() when failing to open a device
workaround for a memory leak in IOHIDManagerCopyDevices()

leaks 192 bytes/call on os x 10.8.2, by scheduling and unscheduling a run loop it doesn't leak.
add better error returns for osx, return the error names, can't find a good strerror() from apple
Add build-aux/ar-lib to .gitignore