Unused variable in curl.c

[wusyong]

It seems there is no reference for the variable int i = 0;. Is it fine to consider remove it? Or does it have any purpose elsewhere?

https://github.com/iotaledger/ccurl/blob/94d74a492a7ff9494c73b7be2dcf80f3ce4d453f/src/lib/curl.c#L74