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.

math: remove 'Created by' lines

A big Thank You to the original contributors of these ports:

  *  Aaron Dalton <aaron@FreeBSD.org>
  *  Aaron Dalton <aaron@daltons.ca>
  *  Alessando Sagratini <ale_sagra@hotmail.com>
  *  Alex Dupre <ale@FreeBSD.org>
  *  Alexey Dokuchaev <danfe@FreeBSD.org>
  *  Amarendra Godbole <amarendra.godbole@gmail.com>
  *  Anders Nordby <anders@FreeBSD.org>
  *  Andreas Fehlner (fehlner@gmx.de)
  *  Andrew L. Neporada <andrew@chg.ru>
  *  Andrey <gugu@zoo.rambler.ru>
  *  Andrey Zakhvatov

Remove # $FreeBSD$ from Makefiles.

math/R: Update to version 4.0.0

Upstream changes:
https://stat.ethz.ch/pipermail/r-announce/2020/000653.html

Also bump PORTREVISION of ports that depend on math/R.

Submitted by:	wen (in part)
Reviewed by:	jwb, Rainer Hurling <rhurlin@gwdg.de>, thierry
Differential Revision:	https://reviews.freebsd.org/D24572

Bump PORTREVISION for ports depending on the canonical version of GCC
as defined in Mk/bsd.default-versions.mk which has moved from GCC 8.3
to GCC 9.1 under most circumstances now after revision 507371.

This includes ports
 - with USE_GCC=yes or USE_GCC=any,
 - with USES=fortran,
 - using Mk/bsd.octave.mk which in turn features USES=fortran, and
 - with USES=compiler specifying openmp, nestedfct, c11, c++0x, c++11-lang,
   c++11-lib, c++14-lang, c++17-lang, or gcc-c++11-lib
plus, everything INDEX-11 shows with a dependency on lang/gcc9 now.

PR:		238330

- Update to 0.2.1

Bump PORTREVISION for ports depending on the canonical version of GCC
defined via Mk/bsd.default-versions.mk which has moved from GCC 7.4 t
GCC 8.2 under most circumstances.

This includes ports
 - with USE_GCC=yes or USE_GCC=any,
 - with USES=fortran,
 - using Mk/bsd.octave.mk which in turn features USES=fortran, and
 - with USES=compiler specifying openmp, nestedfct, c11, c++0x, c++11-lang,
   c++11-lib, c++14-lang, c++17-lang, or gcc-c++11-lib
plus, as a double check, everything INDEX-11 showed depending on lang/gcc7.

PR:		231590

Bump PORTREVISIONs of all users of math/mpc that we just updated to
version 1.1.0 (via revision 464079).

- Update to 0.2.0

assertthat is an extension to stopifnot() that makes it easy to
declare the pre and post conditions that you code should satisfy,
while also producing friendly error messages so that your users
know what they've done wrong.

WWW: https://cran.r-project.org/web/packages/assertthat/