spawn-fcgi: Update to 1.6.4

Changes:

    Use octal mode for -M (patch by dfjoerg)
    Add -b backlog option (fixes #2422, patch by aschmitz)
    Restrict Unix socket file ownership by default to ug=rw
    Add example apparmor spawn-fcgi abstraction
    Use autoreconf instead of calling tools manually
    Add more flags to extra-warning flags
    Check return values of setuid, setgid, setgroups, initgroups, write
    Check whether compiler supports wanted CFLAGS (fixes #2235)
    Fix resource leaks in failure cases (found with coverity)

(nia)