Make this code use the proper pointers

docs/examples/multi-post.c

@@ -24,12 +24,13 @@ int main(int argc, char *argv[])
   CURLM *multi_handle;
   int still_running;
 
-  struct HttpPost *formpost=NULL;
-  struct HttpPost *lastptr=NULL;
+  struct curl_httppost *formpost=NULL;
+  struct curl_httppost *lastptr=NULL;
   struct curl_slist *headerlist=NULL;
   char buf[] = "Expect:";
 
-  /* Fill in the file upload field */
+  /* Fill in the file upload field. This makes libcurl load data from  
+     the given file name when curl_easy_perform() is called. */
   curl_formadd(&formpost,
                &lastptr,
                CURLFORM_COPYNAME, "sendfile",
@@ -43,7 +44,6 @@ int main(int argc, char *argv[])
                CURLFORM_COPYCONTENTS, "postit2.c",
                CURLFORM_END);
 
-
   /* Fill in the submit field too, even if this is rarely needed */
   curl_formadd(&formpost,
                &lastptr,