[groff] Missing -mptx in 1.22.3.

[Ralph Corderoy]

Hi,

groff_tmac(5) says

    ptx    A single macro is provided in this file, xx, for formatting
           permuted index entries as produced by the GNU ptx(1) program.
           In case you need a different formatting, copy the macro into
           your document and adapt it to your needs.

but /usr/share/groff/1.22.3/tmac has no ptx.tmac.

There is a /usr/heirloom/lib/doctools/tmac/ptx from package
heirloom-doctools.

Cheers, Ralph.