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
Previously it was more or less assumed that GSocketConnections were
always connected, although this was not enforced. Make it explicit
that they don't need to be, and add methods to connect them, and
simplify GSocketClient by using those methods.
https://bugzilla.gnome.org/show_bug.cgi?id=665805