Bump fatsd to master (issue #16)

commit 7d9f90ebe9dd3a7f6af1fbb97d8cc228fb0fded4
Author: David Bauer <mail@david-bauer.net>
Date:   Thu Jul 25 18:51:25 2019 +0200

    resolve: fix segmentation fault with musl >1.1.20

    When compiled with musl >1.1.20, fastd will crash in case it can't
    resolve a peers hostname. This is due to a changed implementation of
    freeaddrinfo in musl 1.1.21 onwards.

    This segfault is fixed by not calling freeaddrinfo in case the supplied
    pointer is null.

    Signed-off-by: David Bauer <mail@david-bauer.net>