gnu: knot: Snip more pregenerated nonsource.

gnu: knot: Snip more pregenerated nonsource.

ypbody.c is generated from ypbody.rl by update-parser.sh, both of which
are missing from the release tarball.  Rather than add another git file
to native-inputs, we now build from git and remove the generated files.

This follows up on commit 2b73e50c31a61b5dcef35a1e4b9484d9dbcb0fbc, now
that everyone's finished building it.

* gnu/packages/dns.scm (knot)[source]: Use GIT-FETCH and GIT-FILE-NAME.
[arguments]: Add ‘--enable-fast-parser’ to #:configure-flags.
Invoke the in-tree update-parser.sh.
[native-inputs]: Remove separate update-parser.sh origin.
Add autoconf, automake, and libtool.