Make the allowed SSL Ciphers a protocol option for CurlFile.

Recent versions of libcurl disable the RC4-SHA cipher that is still used by some sites.
While certainly the right decision, it breaks (at least) the YouTube addon.

This patch allows addons to explicitly request disabled ciphers via a protocol option:
https://host/path|SSLCipherList=DEFAULT:RC4-SHA
Merge pull request #4489 from Orochimarufan/sslcipher

Make the allowed SSL Ciphers a protocol option for CurlFile.