Aravis 0.8.20

• camera: make set_frame_rate more robust for Basler cameras (Thies)
• misc: add runtime version API (Emmanuel)
• misc: ignore leading spaces in genicam data url (Emmanuel)
• misc: add get_device_manufacturer_info API (Emmanuel)
• qa: fix incorrect memory access (Jose)
• gstreamer: allow to select asynchronous USB mode (Christian)
• windows: fix thread priority helpers (Garfeng)
• meson: fix compilation using meson 0.60 (Emmanuel)
• doc: ubuntu 20.04 build do cimprovements (Brian)