KDE: update WWW for meta ports

multimedia/kdemultimedia: update dependency line for kdenlive

KDE: It goes to 6!

This megacommit merges all the work from
https://github.com/freebsd/freebsd-ports-kde/tree/kde-it_goes_to_6
Specifically:
- KDE Plasma 6 ports updated to 6.2.5
- KDE Applications ports updated to 24.12.0
- Development ports of KDE Applications removed
- A lot of various ports switched to Qt 6 by default
- Some KDE Frameworks 5 and Plasma 5 ports are adapted to be coinstallable
  with their 6 counterparts

PR:		284351
Exp-run by:	antoine
Pull Request:	https://github.com/freebsd/freebsd-ports/pull/341

Co-authored-by:	Max Brazhnikov <makc@FreeBSD.org>
Co-authored-by:	Kenneth Raplee <kenrap@kennethraplee.com>
Co-authored-by:	Jason E. Hale <jhale@FreeBSD.org>
Co-authored-by:	Gleb Popov <arrowd@FreeBSD.org>

audio/opus: bump consumers after update to 1.4

*: Bump PORTREVISIONs for math/mpc update to 1.3.1

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.

KDE: change default sound mixer applet

The kmix mixer is being replaced by the more flexible and integrated
plasma-pa mixer from audio/plasma5-plasma-pa

For this:

	- remove audio/kmix from the default options set in the metaport
	  multimedia/kdemultimedia

	- add audio/plasma5-plasma-pa to the default options set in the
	  metaport x11/plasma5-plasma

If you do not want pulseaudio on your system and want to keep using
the old mixer, you have multiple options:

	a) don't install the metaports (they only pull in other
	   packages)
	b) manually build multimedia/kdemultimedia and
	   x11/plasma5-plasma with your chosen options
	c) install both

Reported by:		Graham Perrin <grahamperrin@gmail.com>
PR:			258579

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

Remove # $FreeBSD$ from Makefiles.

Update KDE Applications to 19.04.0

The changelog can be found here:
	- https://kde.org/announcements/announce-applications-19.04.0.php

Due to crashes on start, multimedia/kdenlive was kept at 18.12.3 for now.

Update KDE Applications to 18.12.2

[1] https://www.kde.org/announcements/announce-applications-18.12.2.php
[2]
https://www.kde.org/announcements/fulllog_applications-aether.php?version=18.12.2

Fix Qt5 symbol version scripts to put the catch-all clause first.  When
a symbol matches multiple clauses the last one takes precedence.  If the
catch-all is last it captures everything.  In the case of Qt5 libraries
this caused all symbols to have a Qt_5 label while some should have
Qt_5_PRIVATE_API.  This only affects lld because GNU ld always gives the
catch-all lowest priority.

Older versions of Qt5Webengine exported some memory allocation symbols from
the bundled Chromium.  Version 5.9 stopped exporting these [1] but the
symbols were kept as weak wrappers for the standard allocation functions to
maintain binary compatibility. [2][3]  The problem is that the call to the
standard function in these weak wrappers is only resolved to the standard
function if there's a call to this standard function in other parts of
Qt5Webengine, because only then is there a non-weak symbol that takes
precedence over the weak one.  If there's no such non-weak symbol the call

Replace bsd.qt.mk by Uses/qt.mk and Uses/qt-dist.mk

From now on, ports that depend on Qt4 will have to set
	USES=		qt:4
	USE_QT=		foo bar
ports depending on Qt5 will use
	USES=		qt:5
	USE_QT=		foo bar

PR:		229225
Exp-run by:	antoine
Reviewed by:	mat
Approved by:	portmgr (antoine)
Differential Revision:	-https://reviews.freebsd.org/D15540

Add the KDE metaports

* add multimedia/dragon (was missing)
* add the meta ports for the categories
* add x11/kde5 [yeah, we know, there technically is no "KDE 5"]