auto/threads

if [ $USE_THREADS = "rfork" ]; then
    have=NGX_THREADS . auto/have
    have=USE_RFORK . auto/have
    CORE_DEPS="$CORE_DEPS $UNIX_THREADS_DEPS"
    CORE_SRCS="$CORE_SRCS $FREEBSD_RFORK_SRCS"
fi