I had to define a new ```:debug_callback``` callback type in lib/ethon/curls/settings.rb:4 because the prototype for the debugfunction callback is different from the other callbacks currently used:

```C
int curl_debug_callback (CURL *, curl_infotype, char *, size_t, void *);
```
The callbacks for writefunction and headerfunction share the same one:

```C
size_t function( void *ptr, size_t size, size_t nmemb, void *userdata);
```
Am I missing something?