Make kevent a configure option, disbled by default

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

contrib/debian/build.sh

@@ -25,7 +25,7 @@ echo
     --prefix=/usr                     --exec-prefix=			\
     --sysconfdir=/etc                 --localstatedir=/var		\
     --enable-dbus-plugin              --enable-x11-common-plugin	\
-    --enable-alsa-utils-plugin						\
+    --enable-alsa-utils-plugin	      --with-keventd			\
     --with-random-seed=/var/lib/urandom/random-seed			\
     --with-heading="Debian GNU/Linux"