package/dante: needs autoreconf

package/dante: needs autoreconf

We have a patch that touches a .m4 file, so we need to regenerate the
configure script. Otherwise, this is done during the build step, and
some environment variables are thus missing and the build may fail when
the host machine does not have the expected autostuff tools.

Fixes:
    http://autobuild.buildroot.org/results/e37/e37e61bae1d81a7956e2843be70fea84b0bbb64b/
    http://autobuild.buildroot.org/results/f96/f969718402cae71446d6280ec1f66d357a155293/
    ...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>