gnuradio/gnuradio: Release v3.9.4.0

Release v3.9.4.0 is appearing a little early because of a couple of regressions in v3.9.3.0. While we were at it, we pulled in a few more helpful commits from the master branch. This is an API compatible update to GNU Radio 3.9. Code written for 3.9.X versions should compile and link without modification. The ABI is not guaranteed to be compatible, so a rebuild of OOT modules may be necessary. Changes Regressions Fixes Remove #include (C++17 feature) from one file Restore pyqwidget() in gr-qtgui GRC GRC now runs on Fedora 35 ... Gtk initialization checks were too strict Add keyboard shortcuts for zoom Account for scale factor when computing drawing area size Use font size from config for block comments Change type aliasing to allow interleaved short/byte to be connected to vectors of short/byte. Stricter type checking was added previously and caused some blocks to be unconnectable when using these types. Required params no longer default to 0 when left empty. This caused hard-to-find errors. Older flowgraphs that have empty required fields will need to be fixed. Tooltips fixed for categories and modules gr-runtime PMT uses the VOLK allocator for vectors get_tags_in_window() Python wrapper calls the correct function Add --pybind option to gnuradio-config-info to get PyBind11 version gr-blocks Add example for XMLRPC Add a unit test for Message Strobe Fix C++ support for Unpacked to Packed gr-channels RNG seeds are initialized correctly gr-digital Fix yml file for Header/Payload Demux gr-network Suppress warning in tuntap gr-qtgui Remove unusable int type in Number Sink yml Use no_quotes() function in several yml files modtool Hashes can be fixed using modtool using --update-hash-only Use tempfile() instead of /tmp in bindtool and modtool Use static_cast instead of reinterpret_cast in templates Correct broken Python general block template Build system Better check for Boost version Determine the Python prefix more reliably Use GR-specified compiler standard (C++14) in gr-soapy, instead of the SoapySDR standard (C++11) GrPython.cmake is compatible with older cmake Documentation Man pages are in-tree Repair many examples, especially in gr-digital Allow UTF-8 in pydoc templates CI Execute make install during test Add Ubuntu 18.04 test targe