Add printing the LC_LINKER_OPTION load command with llvm-objdump’s -private-headers.

Add printing the LC_LINKER_OPTION load command with llvm-objdump’s -private-headers.
Also corrected the name of the load command to not end in an ’S’ as well as corrected
the name of the MachO::linker_option_command struct and other places that had the
word option as plural which did not match the Mac OS X headers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224485 91177308-0d34-0410-b5e6-96231b3b80d8