glib/gobject-introspection: update 2.78.4 -> 2.80.0, 1.78.1 -> 1.80.0

glib/gobject-introspection: update 2.78.4 -> 2.80.0, 1.78.1 -> 1.80.0

With these versions, which need to be updated in lockstep, upstream has
relocated glib introspection data from g-i tree to glib tree and made
its generation a part of the overall glib build. This creates a circular
dependency, where g-i tools are linked with glib, but glib needs the tools
to build its g-i data. (I don't know why the two source trees
couldn't be simply merged into one, or g-i data for glib couldn't be generated
inside g-i build against sysroot glib).

Upstream is suggesting building glib twice, first without building g-i data,
then building g-i and linking it with that version, then building
the final glib, and that's what is being done here (via the new
glib-initial recipe, which is sysroot-only, and is not pulled in
via indirect dependencies either).

Other glib changes:
0001-Do-not-write-bindir-into-pkg-config-files.patch restores
writing bindir variable into glib.pc file (meson only writes
it out if other variables depend on it, and this custom patch
removes that dependency).

0001-girepository-introspection-correctly-install-.gir-fi.patch
ensures correct installation of .gir into something else
than $datadir (useful in multilib).

Merge previous glib .bb into .inc, so that glib and glib-initial
recipes could be cleanly separated with no duplication.

Convert from gtk-doc to gi-docgen, and manpages from xmlto to
docutils.

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