curl: fix callback argument inconsistency

As you can see the callback definition uses a char* for the first
argument, while the function uses a void*.

URL: https://curl.haxx.se/mail/lib-2017-03/0116.html

src/tool_cb_hdr.c

@@ -40,7 +40,7 @@ static char *parse_filename(const char *ptr, size_t len);
 ** callback for CURLOPT_HEADERFUNCTION
 */
 
-size_t tool_header_cb(void *ptr, size_t size, size_t nmemb, void *userdata)
+size_t tool_header_cb(char *ptr, size_t size, size_t nmemb, void *userdata)
 {
   struct HdrCbData *hdrcbdata = userdata;
   struct OutStruct *outs = hdrcbdata->outs;

src/tool_cb_hdr.h

@@ -48,7 +48,7 @@ struct HdrCbData {
 ** callback for CURLOPT_HEADERFUNCTION
 */
 
-size_t tool_header_cb(void *ptr, size_t size, size_t nmemb, void *userdata);
+size_t tool_header_cb(char *ptr, size_t size, size_t nmemb, void *userdata);
 
 #endif /* HEADER_CURL_TOOL_CB_HDR_H */
 

src/tool_cb_wrt.c

@@ -72,7 +72,7 @@ bool tool_create_output_file(struct OutStruct *outs)
 ** callback for CURLOPT_WRITEFUNCTION
 */
 
-size_t tool_write_cb(void *buffer, size_t sz, size_t nmemb, void *userdata)
+size_t tool_write_cb(char *buffer, size_t sz, size_t nmemb, void *userdata)
 {
   size_t rc;
   struct OutStruct *outs = userdata;

src/tool_cb_wrt.h

@@ -27,7 +27,7 @@
 ** callback for CURLOPT_WRITEFUNCTION
 */
 
-size_t tool_write_cb(void *buffer, size_t sz, size_t nmemb, void *userdata);
+size_t tool_write_cb(char *buffer, size_t sz, size_t nmemb, void *userdata);
 
 /* create a local file for writing, return TRUE on success */
 bool tool_create_output_file(struct OutStruct *outs);