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
Add support for a mutex lock that consumes only one bit of storage
inside of an integer on systems that support futexes. Futex is emulated
(at a higher cost) on systems that don't have it -- but only in the
contended case.