Description:
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In order for cURL to use a provided CRL file when verifying peers CURLOPT_CRLFILE has to be set in the form of a char * (available since 7.19) 

This can then be used in the form like 
 curl_setopt($chhkps, CURLOPT_CRLFILE, '/path/to/ca/crl.pem'); 
 curl_setopt($chhkps, CURLOPT_SSL_VERIFYHOST, 2);
 curl_setopt($chhkps, CURLOPT_SSL_VERIFYPEER, true);


Expected result:
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CRL file being validated. As is the behaviour with the provided patch

Actual result:
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Constant CURLOPT_CRLFILE not defined