setopt: less *or equal* than INT_MAX/1000 should be fine

... for the CURLOPT_TIMEOUT, CURLOPT_CONNECTTIMEOUT and
CURLOPT_SERVER_RESPONSE_TIMEOUT range checks.

Reported-by: Dominik Hölzl
Bug: https://curl.haxx.se/mail/lib-2017-12/0037.html

Closes #2173