mlogc: Checks if curl supports CURL_SSLVERSION_TLSv1_2 before use it

Seems like curl versions older than 7.34.0 does not have support for
`CURL_SSLVERSION_TLSv1_2'. In this cases, using CURL_SSLVERSION_TLSv1
which was added at version 7.9.2. ModSecurity demands a curl version
newer than 7.15.1.