Update to 5.6 release

    - debian/patches/api_startup.patch: Upstreamed.
    - debian/patches/git-07ecca2240c680373e9c2e5e38241edde9d1a677: Upstreamed.
    - debian/patches/brldefs-install.patch: Upstreamed.
    - debian/patches/git-ba42441d03c6145fe6859c90fb01b1fa16221a2f: Upstreamed.
    - debian/brltty-udeb.udev.rules: Add new device IDs.
    - debian/control: Add liblouis-dev build-dep.
    - debian/rules: Make brltty install appstream data.