commit 617ba838746287974505c6a9c4de6c65172ea112
Author: chux0519 <chuxdesign@hotmail.com>
Date:   2021-01-09 17:19:27 +0800

    evdns: add max-probe-timeout/probe-backoff-factor settings
    
    I recently found that when the network status changed when calling
    bufferevent_socket_connect_hostname (e.g. switching between several
    WIFIs), all DNS servers would fail, and the timeout of probe would be
    very long if there were many DNS requests. I want libevent to support
    manual setting of MAX_PROBE_TIMEOUT and TIMEOUT_BACKOFF_FACTOR
    
    So move hardcoded MAX_PROBE_TIMEOUT and TIMEOUT_BACKOFF_FACTOR into
    struct, and allow changing them.

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