Restrict CURLOPT_PROTOCOLS on defined() instead of version_compare()

[ozh]

Instead of setting CURLOPT_PROTOCOLS upon a version_compare(), why not simply do it upon a defined?

Besides of being simpler, it might

• cope with potential weird builds of libcurl showing a recent version but not implement that option?
• fix the Travis errors when using HHVM ?

[coveralls]

Coverage remained the same when pulling 6856025 on ozh:curlopt into 14b5f32 on rmccue:master.

[ozh]

Eh, better regarding Travis, although not fixed yet :)

[rmccue]

Interesting error with HHVM now, but way better than before in any case. Thanks! :)

[rmccue]

Also worth mentioning that while this looks worse (OMG fatal error!), it fixes the main issue before and doesn't cause any new ones. :)