Minor changes to build under Debian 11.
requested to merge jonathan-hanks/advligorts:255_update_cmake_and_code_to_build_both_buster_and_bullseye into master
- Reorder Python and PyBind11 in the cmake.
- Add a daqd/comm.hh as bison wants to read that instead of y.tab.h.
- Adding the header to a few places.
- Minor reworking on Boost::ASIO code in passing around io_contexts.
Work towards #255