Broken build on OpenBSD

Hi Simon,

Commit c5819701a3de61e2ba2ef7ad0b616565b32305e5 broke the build on OpenBSD and probably other non-Linux systems. ENODATA, which is now used in fit_check_format(), isn't defined. It isn't part of POSIX[1] and generally not available on BSD-derived systems. Could you pick another error code for this case?

Thanks,

Mark

[1] It is mentioned in the Open Group Base Specification, however it is part of the obsolete XSI STREAMS extension which was never part of POSIX proper.