GUPnP 0.20.5 Adds Simple Network Device Whitelisting Infrastructure

GUPnP 0.20.5 adds simple network device whitelisting infrastructure, adds various missing G_{BEGIN,END}_DECLS guards, ports gupnp-binding-tool to Python 3, upgrades gtk-doc stuff, enables GTest tests, and removes the test for inverted arguments in the GUPnPContext tests. GUPnP 0.20.5 also fixes the uninitialized variable use introduced in the previous version, fixes crashes in NetworkManager’s context manager during some async calls, fixes a small memory leak in the UNIX and Windows CM, and repairs the service example in documentation.