xf86-video-wsfb: Add support for Nintendo Wii

The Wii's framebuffer is YUY2, so add a custom shadowproc that converts
from RGB565 to YUY2 on the fly.

wsfb: reduce diffs from upstream.

Mostly pulled/merged from the following upstream changes:

- Fix for dlopen() -based module loader.
https://gitlab.freedesktop.org/xorg/driver/xf86-video-wsfb/-/commit/b77092858a178aa169ed4c1c7fe733d5cd355702

- Remove useless loader symbol lists.
https://gitlab.freedesktop.org/xorg/driver/xf86-video-wsfb/-/commit/bce9fd21483fbeddc84672a1ef01fdd9b58c88ed

- Add compat-api.h for compatibility with xserver 1.13
https://gitlab.freedesktop.org/xorg/driver/xf86-video-wsfb/-/commit/586b722fb17b3eb0ab776c170ee21e6a66fc7f22

- Use own thunk functions instead of shadow*Weak
https://gitlab.freedesktop.org/xorg/driver/xf86-video-wsfb/-/commit/fa9aabe95a65c4dd12008e16ad66d5c773a7993a

- Remove obsolete #ifdef HAVE_XF1BPP and #ifdef HAVE_XF4BPP blocks,
https://gitlab.freedesktop.org/xorg/driver/xf86-video-wsfb/-/commit/16ac29883cb80053fb0b973166a3f664cae1fa44

- Remove unused variables
https://gitlab.freedesktop.org/xorg/driver/xf86-video-wsfb/-/commit/1c1bf30b612933a3303d414c75671c9a05ec450a

- Suppress a bunch of compiler warnings for using constant strings
https://gitlab.freedesktop.org/xorg/driver/xf86-video-wsfb/-/commit/1ff2e87ea1c19d1417b11886d940e205be376d78

- Replace LoaderGetOS with ifdef
https://gitlab.freedesktop.org/xorg/driver/xf86-video-wsfb/-/commit/8069c6970c731c38e105f5dddd5ce83ba88b0773

- Fix spelling/wording issues
https://gitlab.freedesktop.org/xorg/driver/xf86-video-wsfb/-/commit/27c2d76404c7b440a6662446b189fa257c4cebfc

With minor adjustments:
- sync order of members in private struct WsfbRec
- add more const to avoid warning
- add newlines properly to xf86Msg() messages

No particular objection on tech-x11@:
https://mail-index.netbsd.org/tech-x11/2022/06/thread1.html#002311

wsfb: reorganize implementation of Afb support.

- use XORG_VERSION_NUMERIC() to check if Afb is avaiable and
define and use explicit HAVE_SHADOW_AFB macro
- disable all Afb references if it is not available

Reviewed on tech-x11@:
https://mail-index.netbsd.org/tech-x11/2022/08/23/msg002311.html

"Looks like good improvement" from jandberg@ and also confirmed by rin@.

various updates to build against xorg-server 21.1.3.

- avoid a const issue with an expanded __UNCONST().
- cope with renamed member names
- deal with "xf86RamDac.h" going away (now use "xf86Cursor.h")

Add support for 8bpp with Amiga native graphics.

Conversion to bitplane format is done in shadowfb update proc.

port xf86-video-wsfb to compat-api.h style interfaces

add a shadowfb update function which endian-swaps 32bit pixels, use if we
have hardware with BGRA pixel format ( like a wrong-endian ARGB framebuffer )
with this applications that use xrender work properly on things like mgx in
32bit colour

use WSDISPLAYIO_GET_FBINFO if available

Enable shadowFB for rotate option.

xf86_ansic.h is no more.
use <errno.h> and <sys/mman.h> always.
remove no longer working 1 and 4 bpp. :-(

add hw cursor support and unbork shadow fb support.
TODO: find out how shadow fb is supposed to work in Xorg