lang/mono: switch to 5.20 by default

PR:		238089

lang/mono: respect MONO_DEFAULT in consumers

PR:		251795

lang/mono*: add compat symlink for devel/msbuild < 16

/usr/local/lib/mono/msbuild/15.0/bin/Microsoft.CSharp.CurrentVersion.targets(331,5):
error MSB4019: The imported project
"/usr/local/lib/mono/msbuild/15.0/bin/Roslyn/Microsoft.CSharp.Core.targets" was
not found. Confirm that the path in the <Import> declaration is correct, and
that the file exists on disk.

PR:		256342
Suggested by:	Marcin Cieślak
Regressed by:	https://github.com/mono/mono/commit/1717687e16dd

*/*: Release ports from maintainership

Maintainer releases all his ports.

PR:		266871
Reported by:	unrelentingtech <greg@unrelenting.technology>

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.

cleanup: drop support for EOL FreeBSD 11.X

Search criteria used:
- 11.4
- OSREL*
- OSVER*
- *_FreeBSD_11

Input from:
- adridg: devel/qca-legacy
- jbeich: _WITH_DPRINTF, _WITH_GETLINE, GNU bfd workarounds
- sunpoet: security/p5-*OpenSSL*

Reviewed by:	doceng, kde, multimedia, perl, python, ruby, rust
Differential Revision: https://reviews.freebsd.org/D32008
Test Plan: make index

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

Remove # $FreeBSD$ from Makefiles.

Mark various ports as BROKEN with Mono 5.20, and, in some other cases,
Mono 6.8.

PR:		238089
Submitted by:	cem
Obtained from:	lonesome.com build regression testing

Bump portrevision for devel/evdev-proto

Bump portrevision on everything with a build dependency on
devel/evdev-proto, to chace the update of evdev-proto in r550442.

e*: Add missing USES={gnome,sdl,xorg}

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

emulators/mesen: add new port

PR:		227351
Submitted by:	Greg V <greg@unrelenting.technology>