webkitgtk: update 2.36.7 -> 2.38.2

Upstream has rewritten gobject introspection support,
so the two related patches are ported to that:
0001-FindGObjectIntrospection.cmake-prefix-variables-obta.patch
0001-When-building-introspection-files-do-not-quote-CFLAG.patch
The latter patch is also promoted from Inappropriate to Pending

gtk-doc has been replaced with gi-docgen, accordingly
0001-Tweak-gtkdoc-settings-so-that-gtkdoc-generation-work.patch is removed.

Drop
fix-gstreamer-include-paths.patch
(backport)
0001-Fix-build-without-opengl-or-es.patch
(upstream fixed the issue; follow the link in the patch for details)

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>