use the correct struct name in the example

docs/libcurl/curl_formadd.3

@@ -129,8 +129,8 @@ defines.
 .SH EXAMPLE
 .nf
 
- struct HttpPost* post = NULL;
- struct HttpPost* last = NULL;
+ struct curl_httppost* post = NULL;
+ struct curl_httppost* last = NULL;
  char namebuffer[] = "name buffer";
  long namelength = strlen(namebuffer);
  char buffer[] = "test buffer";