Multiline @cindex entries misrender in groff Texinfo manual

[Dave Kemper]

In a few places, the groff Texinfo manual uses a line-ending @ to
continue a @cindex entry.  An example is:

  @DefreqList {tm, message}
  @DefreqItemx {tm1, [@code{"}]message}
  @DefreqListEndx {tmc, [@code{"}]message}
  @cindex print to the standard error stream (@code{tm}, @code{tm1},@
  @code{tmc})
  @cindex standard error stream, write to (@code{tm}, @code{tm1},@
  @code{tmc})
  @cindex stream, standard error, write to (@code{tm}, @code{tm1},@
  @code{tmc})
  Send @var{message}, which consumes the remainder of the input line and

My version of makeinfo (texi2any (GNU texinfo) 6.7) doesn't render
this as desired:

  -- Request: .tm message
  -- Request: .tm1 ['"']message
  -- Request: .tmc ['"']message
      'tmc') 'tmc') 'tmc') Send MESSAGE, which consumes the remainder of
      the input line and ...

That is, the continued @code{} tags are being put into the output
rather than considered part of the index entry.

I don't know enough about the Texinfo language to know whether this is
a bug in our manual or in makeinfo.  Does this render correctly in
newer makeinfo versions?  makeinfo 6.7 is fairly old, but the groff
manual appears to require only 5.0 (as of commit 986d2a5b2, Apr 2020
(http://git.savannah.gnu.org/cgit/groff.git/commit/?id=986d2a5b2)).