Remove WWW entries moved into port Makefiles

Commit b7f05445c00f has added WWW entries to port Makefiles based on
WWW: lines in pkg-descr files.

This commit removes the WWW: lines of moved-over URLs from these
pkg-descr files.

Approved by:		portmgr (tcberner)

Add WWW entries to port Makefiles

It has been common practice to have one or more URLs at the end of the
ports' pkg-descr files, one per line and prefixed with "WWW:". These
URLs should point at a project website or other relevant resources.

Access to these URLs required processing of the pkg-descr files, and
they have often become stale over time. If more than one such URL was
present in a pkg-descr file, only the first one was tarnsfered into
the port INDEX, but for many ports only the last line did contain the
port specific URL to further information.

There have been several proposals to make a project URL available as
a macro in the ports' Makefiles, over time.

lang/python2: Clean up

- Remove leading definite article from COMMENT
- Remove unneeded use of PYTHON_MAJOR_VER because this is for python 2.7

One more small cleanup, forgotten yesterday.
Reported by:	lwhsu

Remove # $FreeBSD$ from Makefiles.

Garbage collecte unusable things from lang/python{,2,3} metaports.

Simplify the lang/python{2,3} metaports.

Reviewed by:	antoine

Deprecate python2

With hat:	portmgr

Drop the ipv6 virtual category for l* category as it is not relevant anymore

Add a not to a few meta ports: do not depend on these ports

Add NO_ARCH

Update WWW

Remove PYTHON*_DEFAULT_VERSION.

Remove dead PYTHON_NO_DEPENDS. It has not been needed or supported since
USES=python was added in r364450.

- Convert ports of irc/ and lang/ to new USES=python

Approved by:	portmgr (implicit)

Remove support for pkg_install
Merge back bsd.pkgng.mk into bsd.port.mk
Add a note about @stopdaemon not being supported anymore

With hat:	portmgr
Differential Revision:	https://reviews.freebsd.org/D693

- Fix and remove stale symlinks after the lang/python* cleanup

Reported by:	Scott Allendorf <scott-allendorf@uiowa.edu>

- Do not use absolute source paths for the symlinks to the stagedir

Noticed by:	danfe

- Enable stagedir support

Install python[23].pc files for the lang/python[23] ports.

Discussed with:	koobs@
Approved by:	python@ (wg@)

Add NO_STAGE all over the place in preparation for the staging support (cat:
lang)

- Introduce PYTHON2_DEFAULT_VERSION, the version of the default python2
  binary in $PATH. It can be set in case the user wants to use a
  specific python2 version as a default. Its behaviour is similar
  to the existing PYTHON3_DEFAULT_VERSION and fixes a small issue with
  package builds for different python versions.
- Outline that PYTHON_DEFAULT_VERSION always takes precedence for a
  specific python major version.
- Update lang/python2 to use PYTHON2_DEFAULT_VERSION and bump the
  PORTREVISION to let the installed port catch up with the change.
- Allow PYTHON3_DEFAULT_VERSION to overriden by a user choice, if
  PYTHON_DEFAULT_VERSION is not set to a python3 port.

Reported by:	David Demelier <demelier.david@gmail.com>
Reviewed by:	koobs@, sbz@
With hat on:	python@

- improve the python meta port descriptions

Requested by:	demon@
Reviewed by:	demon@

- Avoid circular dependencies due to the previous bsd.python.mk change

- Move the symlink magic for the default python version into lang/python
  and lang/python2 and lang/python3. This change brings us closer to the goal
  of making Python ports usable with different Python versions at the same
  time.
- Add a new lang/python2 port to handle the symlinks for bin/python2,
  bin/idle2, bin/pydoc2 and so on.
- Add a new lang/python3 port to handle the symlinks for bin/python3,
  bin/idle3, bin/pydoc3 and so on.
- Bump the PORTREVISION on all lang/python* ports.