package/webkitgtk: security bump to version 2.22.5

package/webkitgtk: security bump to version 2.22.5

This is a maintenance release of the current stable WebKitGTK+ version,
which contains security fixes for CVE identifiers: CVE-2018-4437,
CVE-2018-4438, CVE-2018-4441, CVE-2018-4442, CVE-2018-4443, and
CVE-2018-4464. Additionally, it fixes a couple of build failures in
unusual build configurations.

Release notes can be found in the announcement:

  https://webkitgtk.org/2018/12/13/webkitgtk2.22.5-released.html

More details on the issues covered by security fixes can be found
in the corresponding security advisory:

  https://webkitgtk.org/security/WSA-2018-0009.html

Signed-off-by: Adrian Perez de Castro <aperez@igalia.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>