Fix crash on 32bit architectures where time_t is 64 bit

This is an ABI change on platforms where sizeof(time_t) doesn't equal
sizeof(long). For most platforms this change shouldn't make a difference
at present. OpenBSD recently switched to 64bit time_t on all architectures
to avoid time_t overflow in 2038 on 32bit machines.

This fix extends to consumers of startup-notification, for instance
the window manager of XFCE, which is how I got involved in this.
See http://mail.xfce.org/pipermail/xfce4-dev/2014-February/030611.html
and follow-ups. The XFCE devs pointed out that my patch to fix a
crash in XFCE's window manager depends on this startup-notification patch.

Signed-off-by: Julien Danjou <julien@danjou.info>
Add include of <sys/select.h> for previous patch

Unfortunately while the standard says that <sys/types.h> is the
correct header to get suseconds_t, at least with glibc, that requires
-DXOPEN_SOURCE.  Which is problematic for a public header, because
then all *users* of startup-notification will be required to define
that.

Poking around a bit, it looks like at least with glibc, <sys/select.h>
will give us an unconditional define.

Signed-off-by: Julien Danjou <julien@danjou.info>
autogen.sh: Honor NOCONFIGURE=1

See http://people.gnome.org/~walters/docs/build-api.txt

Signed-off-by: Julien Danjou <julien@danjou.info>