Fix curl's version verification

Oops, something went awfully wrong ; we need to change to constant only if we have a version __below__ (and not __below *or equal*__), and while we're at it, divide the timeout by 1000 rather than multiplying it by 1000. We want seconds, not nanoseconds !
Fix version_compare usage
Merge pull request #51 from Taluu/fix-curl-verif

Fix curl's version verification