basicfuncs-plus: Disable $(state) when glib is too old

When compiling on systems with glib older than 2.32, disable the
$(state) template function, because that requires features not present
in earlier versions. This fixes #4.

Reported-by: Peter Czanik <czanik@balabit.hu>
Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>