webkitgtk: update 2.38.5 -> 2.40.2

Drop backports.

Add extra options that require additional dependencies, and fail without them.

Disable the recipe on ancient x86 without SSE support; SSE is now
required.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>