adding dnstap to documentation

doc/build.rst

@@ -56,6 +56,9 @@ There are also *optional* packages that enable specific functionality in Knot DN
    "Sphinx_ and sphinx_rtd_theme_", "``documentation``", "Building this HTML/PDF documentation."
    "breathe_", "``documentation``", "Exposing Doxygen API doc to Sphinx."
    "libsystemd_", "``daemon``", "Systemd socket activation support."
+   "libprotobuf_ 3.0+", "``modules/dnstap``", "Protocol Buffers support for dnstap_."
+   "`libprotobuf-c`_ 1.0+", "``modules/dnstap``", "C bindings for Protobuf."
+   "libfstrm_ 0.2+", "``modules/dnstap``", "Frame Streams data transport protocol."
 
 .. [#] Requires C99, ``__attribute__((cleanup))`` and ``-MMD -MP`` for dependency file generation. GCC, Clang and ICC are supported.
 .. [#] You can use variables ``<dependency>_CFLAGS`` and ``<dependency>_LIBS`` to configure dependencies manually (i.e. ``libknot_CFLAGS`` and ``libknot_LIBS``).
@@ -293,5 +296,9 @@ You can hack on the container by changing the container entrypoint to shell like
 .. _deckard_doc: https://gitlab.labs.nic.cz/knot/resolver/blob/master/tests/README.rst
 
 .. _libsystemd: https://www.freedesktop.org/wiki/Software/systemd/
+.. _dnstap: http://dnstap.info/
+.. _libprotobuf: https://developers.google.com/protocol-buffers/
+.. _libprotobuf-c: https://github.com/protobuf-c/protobuf-c/wiki
+.. _libfstrm: https://github.com/farsightsec/fstrm
 
 .. _DESTDIR: https://www.gnu.org/prep/standards/html_node/DESTDIR.html