dbus: bump to version 1.12.0

Remove --enable-abstract-sockets; dropped upstream. Remove
ac_cv_have_abstract_sockets that is dropped as well.

Remove --disable-selinux; we handle selinux as an optional dependency
below.

Remove --{enable,disable}-dnotify; this options has been removed in
version 1.7.6, broken since 2010.

Remove --with-init-scripts; dropped upstream.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>