Add error checking for Mach-O universal files.

Add the checking for both the MachO::fat_header and the
MachO::fat_arch struct values in the constructor for
MachOUniversalBinary. Such that when the constructor
for ObjectForArch is called it can assume the values in
the MachO::fat_arch for the offset and size are contained
in the file after the MachOUniversalBinary constructor
is called for the Parent.

llvm-svn: 288084