Mk/bsd.port.mk: move WWW to Makefile

[tcberner]

Summary

The WWW of a port was previously read from pkg-descr using a call to
awk during make describe. This change will read the new variable WWW
defined in the ports Makefile instead.

The ports tree can be converted using a script to move all the 'WWW:'
form their previous location in pkg-descr to the correspodning
Makefiles.

[bapt]

LGTM

[se]

As previously discussed with Tobias, I had already worked out similar changes but did not create a review since I did not expect any reviewer to even take a look ...
My patches for this feature were slightly different but had the same effect:

• I had kept the parsing of the pkg-descr file in case the WWW variable was not defined in some port's Makefile (in order to ease the transition).
• I had made the "www-site" target just echo "${_WWW}" in case "make www-site" is used in some user's script.

Changes to documentation and other ports required to support the "WWW in Makefile" feature:

• The documentation (Porter's Handbook) needs to be adjusted to mention "WWW=" in the Makefile instead of "WWW:" in the pkg-descr file.
• The WWW macro should be introduced to "portlint", "portfmt", and "portclippy" (probably more).

If the WWW line is actually removed from pkg-descr of the ports, it should perhaps be appended to the copy of pkg-descr included in the package files - there might be down-stream tools that expect the WWW line to exist (instead of fetching this information from the MANIFEST).

Mk/bsd.port.mk

123

I'd suggest to move the definition of "WWW" to immediately follow "COMMENT" since it allows to access information about the port beyond the short description provided by ${COMMENT}.

4404

This definition of _WWW creates bogus URLs e.g. for all USE_GITHUB ports - I'm not convinced that this is a useful default value.
My version of this patch kept the parsing of the pkg-descr file in case ${WWW} was not defined, in order to allow non-converted port definitions to still be supported.

4440

I'd keep this target and would just echo the WWW variable.

[tcberner]

possible helper script to move WWW:
https://people.freebsd.org/~tcberner/patches/move_www_to_makefile.rb