Fix a bug in llvm-objdump’s -private-headers for 32-bit Mach-O files
printing the section header.  And add some tests for this for 32-bit files.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224302 91177308-0d34-0410-b5e6-96231b3b80d8