ports/128726: [NEW PORT] print/lyx16: Document processor interfaced with LaTeX (nearly WYSIWYG) (version 1.6)

[Koji Yokota]

I think the problem is that print/lyx16 (and print/lyx15) requires Qt4.
 Is it already acceptable to set an application that requires Qt4 as
standard?

Another point is that there will be another release from lyx-1.5.x
stream. lyx16 is an overhaul from the previous version and it cannot be
excluded that it may contain a lot of bugs. So, prudent users may want
to use lyx15 for a while.