Log Message:
Remove guile16.

Guile has had multiple versions in pkgsrc because of compatibility
problems, starting with 1.4.  Currently, 1.8 is the stable version and
2.0 the new version in pkgsrc, even though in the regular world 1.8 is
old and 2.0 is stable.  As far as I know, no one uses guile 1.6 any
more, and it has no depending packages in pkgsrc (tex2page was the
last one).