gnu: opendht: Add patch.

gnu: opendht: Add patch.

The 2.1.4 release of opendht contains a bug, preventing it's use with recent
releases of Jami.  This minor patch [1] resolves this issue, and should be
possible to remove with the next release.

1: https://github.com/savoirfairelinux/opendht/commit/e2b39dd3a0742853e00f9c3e8c46c911da20bed7

* gnu/packages/patches/opendht-fix-jami.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/networking.scm (opendht)[source]: Apply the patch.

Signed-off-by: Christopher Baines <mail@cbaines.net>