Declare void functions as such
Declare void functions as such

handle_a11y_enabled_changed was missing a 'static void', causing
static analyzers to complain about returns.

https://bugzilla.gnome.org/show_bug.cgi?id=662249

GNOME/at-spi2-core,GNOME/at-spi2-core,GNOME/at-spi2-core