clarify meaning of PORTDOCS

[Dmitry Marakasov]

Hi!

I'm a bit confused with the meaning of PORTDOCS variable. It's
description state that it should not be used if NOPORTDOCS is
defined. But as far as I can judge from bsd.port.mk, PORTDOCS is not
ever accessed if NOPORTDOCS is defined. So should I check for NOPORTDOCS
when I define PORTDOCS?

I thing it would be better to change it's meaning to "list of
documentation files installed in unless NOPORTDOCS is defined", thus
getting rid of extra !defined(NOPORTDOCS) checks in Makefiles. I would
sumbit a PR for this right away, but there's bsd.ocaml.mk which still
uses PORTDOCS without checkinf NOPORTDOCS, and I'm not sure how to
change it in correct way. Thus, cc bsd.ocaml.mk maintainer.

-- 
Dmitry A. Marakasov    | jabber: amdmi3 at jabber.ru
amdmi3 at amdmi3.ru       | http://www.amdmi3.ru