All gobject/*.{c,h} files have been processed.

gmarshal.c and gmarshal.h don't have a license header.

https://bugzilla.gnome.org/show_bug.cgi?id=776504

Add various (nullable) and (optional) annotations which were missing
from a variety of functions. Also port a couple of existing (allow-none)
annotations in the same files to use (nullable) and (optional) as
appropriate instead.

Secondly, add various (not nullable) annotations as needed by the new
default in gobject-introspection of marking gpointers as (nullable). See
https://bugzilla.gnome.org/show_bug.cgi?id=729660.

This includes adding some stub documentation comments for the
assertion macro error functions, which weren’t previously documented.
The new comments are purely to allow for annotations, and hence are
marked as (skip) to prevent the symbols appearing in the GIR file.

https://bugzilla.gnome.org/show_bug.cgi?id=719966

Add the GLIB_AVAILABLE_IN_ALL annotation to all old functions (that
haven't already been annotated with the GLIB_AVAILABLE_IN_* macros or a
deprecation macro).

If we discover in the future that we cannot use only one macro on
Windows, it will be an easy sed patch to fix that.

https://bugzilla.gnome.org/show_bug.cgi?id=688681

gcc has optimizations for include guards that only work
if they are outermost in the the header.
https://bugzilla.gnome.org/show_bug.cgi?id=689810

Just like the rest of the GValueArray API.

The GValueArray type was added in a time, during the Jurassic era or so,
when GArray did not have a representable GType. The GValueArray API has
various issues as well:

  - it doesn't match the other GLib array types;
  - it is not reference counted;
  - the structure is fully exposed on the stack, so it cannot be
    extended to add reference counting;
  - it cannot be forcibly resized.

The nice thing is that now we have a GArray type that can replace in
full GValueArray, so we can deprecate the latter, and reduce the
complexity in GLib, application code, and bindings.

https://bugzilla.gnome.org/show_bug.cgi?id=667228

This will let others opt out of seeing GLib deprecation warnings
by defining GLIB_DISABLE_DEPRECATION_WARNINGS.

https://bugzilla.gnome.org/show_bug.cgi?id=661438