qt-webkit-kiosk: bump to version 1.99.6-8-g26e3085

This bumps the package from 1.99.3 to 1.99.6 (stability fixes), plus a
few documentation changes and a fix for the build issue logged at [1].

[1] http://autobuild.buildroot.net/results/9ac/9acb15f955b8af31a3beeb0bd84c4b0db495e354/



Signed-off-by: Jérôme Oufella <jerome.oufella@savoirfairelinux.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>