Another additional error check for invalid Mach-O files for the

Another additional error check for invalid Mach-O files for the
obsolete load commands.

Again the philosophy of the error checking in libObject for
Mach-O files, the idea behind the checking is that we never
will return a Mach-O file out of libObject that contains unknown
things the library code can’t operate on.  So known obsolete
load commands will cause a hard error.

Also to make things clear I have added comments to the
values and structures in Support/Mach-O.h and
Support/MachO.def as to what is obsolete.

As noted in a TODO in the code, there may need to be a
non-default mode to allow some unknown values for well
structured Mach-O files with things like unknown load
load commands.  So things like using an old lldb on a newer
Mach-O file could still provide some limited functionality.

llvm-svn: 285342