Sub-directories inside gio/ already processed in a previous commit:
- fam/
- gdbus-2.0/ (which contains only codegen/)
- gvdb/
- inotify/
- tests/
- win32/
- xdgmime/

Other sub-directories inside gio/:
- completion/: no license headers
- kqueue/: not LGPL, BSD-style license

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

Commit e7fd3de86d60 already did most of this.

https://bugzilla.gnome.org/show_bug.cgi?id=728285

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

gio/gproxyresolver.h: GProxyResolver already documented in gio/giotypes.h
gio/gtlsbackend.h: GTlsBackend already documented in gio/gtlsbackend.c
gio/gtlsclientconnection.h: GTlsClientConnection already documented in gio/gtlsclientconnection.c
gio/gtlsconnection.h: GTlsConnection already documented in gio/gtlsconnection.c
gio/gunixconnection.h: GTcpConnection already documented in gio/giotypes.h
glib/gversion.h: GLIB_CHECK_VERSION already documented in glib/gversion.c

Found these thanks to the improved gobject-introspection
GTK-Doc comment block/annotation parser.
See https://bugzilla.gnome.org/show_bug.cgi?id=672254

https://bugzilla.gnome.org/show_bug.cgi?id=673385

This extension point allow extending GLib with library like LibProxy that
interprets system proxy settings and finds the appropriate configuration
based on the type of connection being made.

Reviewed-by: Dan Winship <danw@gnome.org>