Range is set improperly for S3_copy_object_range.

[JustinKyleJames]

Shouldn't the end range for the following be params->startByte + params->byteCount - 1?

I am getting an error because of an attempt to write one byte beyond the file.

https://github.com/bji/libs3/blob/287e4bee6fd430ffb52604049de80a27a77ff6b4/src/request.c#L404-L406