Use %autosetup, %make_build, and %make_install macros
    
    Using %autosetup removes the need to manually define %patchN macros.
    
    Using %make_build and %make_install handles %{?_smp_mflags} and DESTDIR.
    
    Also remove cruft related to the znc systemd service file install, left
    after a53b3b8 ("cleanup conditionals, use upstream unit file",
    2016-10-07).