set getOpt function arg is optional

[chanble]

curl_getinfo function's second argument is optional , when I want get all curl info, I can't do it, so I think getOpt function is also.

[nadar]

I would recommend to create another functions which does this, like getOpts() this way the api of the library is more clear.

[nadar]

@amouhzi i would suggest to create another function. So either close, create new PR or merge.