No support for SSL/TLS connections with HHVM

[clue]

HHVM does not (currently) implement the required stream_socket_enable_crypto() function (facebook/hhvm#1647).

Trying to establish a SSL/TLS connection via the SecureConnector results in a fatal error:

Fatal error: Call to undefined function stream_socket_enable_crypto() […]

Opening this ticket as a reminder and for reference in related issues.

[clue]

Until HHVM adds support we may want to look into providing a workaround to at least fail gracefully.

Checking for the existence of the function and rejecting the promise would probably be the least invasive way that does not involve a BC break.

[flip111]

This has been implemented since hhvm 3.8 https://github.com/facebook/hhvm/blob/HHVM-3.8/hphp/runtime/ext/stream/ext_stream.cpp#L690