S390: Hotpatching fixes.

 * Properly align function labels with -mhotpatch and add test cases.
 * Include the nops after the function label in the area covered by cfi and
   debug information.
 * Correct a typo in the documentation.
 * Fix formatting in the generated 6-byte-NOP and adapt the test cases.

Ciao

Dominik ^_^  ^_^

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Dominik Vogt
IBM Germany