gnuradio: Update to 3.6.5. Also fix for docs, packaging, and grc RDEPENDS.

* Fix packaging so grc and examples packages are not empty.
* Account for addition of gr-modtool.
* Update to version 3.6.5 of GNU Radio.
* Update RDEPENDS for grc to add python-netserver.
* Try even harder to stop docs from getting built.

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Philip Balister <philip@balister.org>