HEADS-UP: Upcoming move of WWW definitions in all ports

PortMgr has just accepted a change that has been in the making for some time:

The move of the "WWW:" entries at the end of the ports' pkg-descr files into
the ports' Makefiles in the form of "WWW=" definitions.

The WWW lines will be put into the maintainer block, immediately following
the MAINTAINER and COMMENT lines.

If there is more than one WWW: line a pkg-descr file, one URL will be
selected to be moved into the Makefile, the other URLs will get a label
"See also:" instead of "WWW:".

The following are examples taken from some port before and after the planned
conversion:

------------------------------------------------------------------------------
libmspack is a portable library for some loosely related Microsoft compression
formats.

WWW: https://www.cabextract.org.uk/libmspack/
WWW: https://github.com/kyz/libmspack
------------------------------------------------------------------------------

This pkg-descr file would be converted to:

------------------------------------------------------------------------------
libmspack is a portable library for some loosely related Microsoft compression
formats.

See also: https://github.com/kyz/libmspack
------------------------------------------------------------------------------

The WWW: entry that is deleted from pkg-descr will be moved into the Makefile:

MAINTAINER=	sunpoet@FreeBSD.org
COMMENT=	Library for Microsoft compression formats
WWW=		https://www.cabextract.org.uk/libmspack/


There will be a total of 4 commits to the ports and docs repositories:

1) This update adds support for the WWW= field in Makefiles.
    It is based on a patch submitted by tcberner in review D34979.

	https://reviews.freebsd.org/D36434

2) Documentation change for the English language version of the porter's
    handbook.

	https://reviews.freebsd.org/D36369

3) Update of all ports' Makefiles to add the "WWW=" entry.

4) Update of all pkg-descr files to remove WWW: lines moved to the Makefile.


The portlint port will be updated "soonish" to check for this use of WWW=
and it will warn about left over WWW: in pkg-descr files.

These commits are planned for the current week - I'm only waiting for the
portlint update to be pushed to the repository by its maintainer.

There are currently 1256 ports without WWW: entry in the pkg-descr file.
I'll open a PR for each affected maintainer to document the missing entries,
these should be added after the conversion wherever a suitable URL exists.