When an HTTPS request to api.wordpress.org fails, try an insecure HTTP request and issue a warning.

Certain versions of cURL appear to claim OpenSSL support but fail to work. We need to not trap users on older versions while we work this out, and instead fall back to an insecure request.

Merges [25956] to the 3.7 branch.
fixes #25716 for the 3.7 branch.

Built from https://develop.svn.wordpress.org/branches/3.7@25957


git-svn-id: http://core.svn.wordpress.org/branches/3.7@25916 1a063a9b-81f0-0310-95a4-ce76da25c4cd