webkitgtk: bump to version 2.22.2

webkitgtk: bump to version 2.22.2

Release notes:

    https://webkitgtk.org/2018/09/03/webkitgtk2.22.0-released.html
    https://webkitgtk.org/2018/09/20/webkitgtk2.22.1-released.html
    https://webkitgtk.org/2018/09/21/webkitgtk2.22.2-released.html

No corresponding security advisories for 2.22.x have been published.
Nevertheless, due to skipping over versions in the 2.20.x series,
the following 2.20.x advisories apply:

    https://webkitgtk.org/security/WSA-2018-0003.html
    https://webkitgtk.org/security/WSA-2018-0004.html
    https://webkitgtk.org/security/WSA-2018-0005.html
    https://webkitgtk.org/security/WSA-2018-0006.html

This also bumps the required GCC version, due to the WebKit code
now using more modern C++ features which were introduced in version
6.x of the compiler. The dependency is propagated to the midori
package as well. Last but not least, BR2_PACKAGE_WEBP_DEMUX and
BR2_PACKAGE_GST1_PLUGINS_BAD_PLUGIN_MPEGTSDEMUX are selected as
they are unconditionally needed by the newer WebKitGTK+ releases
when multimedia support is enabled.

An upstream patch for 32-bit ARM which did not make it to be included
in this new version is included as well, and can be removed once it
gets picked in a new release.

Signed-off-by: Adrian Perez de Castro <aperez@igalia.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>