MachO Universal Binary is a commonly used format in OS X and iOS, e.g.
frameworks in Apple's iOS SDK. Adding support for MachO Universal Binary
makes llvm-readobj a more convenient tool for the daily use.
And because MachO Universal Binary is rather a container format than binary
format, this patch adds support for handling this format in the same way as
in Archive files, i.e., dumping required information for MachO Objects in it
one by one.