mac-sys-utils:  Add errno_from_mac_error()
MacRelixLib:  Use mac::sys::errno_from_mac_error()
OSErrno:  Use mac::sys::errno_from_mac_error()
Merge branch 'errno_from_mac_error'
mac-sys-utils:  Map fsDSIntErr, badMDBErr to EIO

Both of these were witnessed when an HFS+ filesystem got corrupted.