hand slip when naming objects (trunk only)

hand slip when naming objects (trunk only)

     From a bug report, the text change applied
when you try to give an artifact's name to am item of that artifact's type
would choose a letter from 'a' through 'y' when replacing the randomly
selected target letter.  Rather than fixing the off by one bug which
prevented 'z' from being chosen, this switches to the existing routine
used for mangling engravings.  (Unfortunately the fix is not as simple as
first expected, because wipeout_text() doesn't guarantee to change text
which has spaces in it and all the quest artifact names have those.)