IsPipeliningPossible: only for HTTP

The function that checks if pipelining is possible now requires the HTTP
bit to be set so that it doesn't mistakenly tries to do it for other
protocols.

Bug: http://curl.haxx.se/mail/lib-2010-12/0152.html
Reported by: Dmitri Shubin

lib/url.c

@@ -2738,12 +2738,14 @@ static bool RTSPConnIsDead(struct connectdata *check)
 }
 #endif /* CURL_DISABLE_RTSP */
 
-static bool IsPipeliningPossible(const struct SessionHandle *handle)
+static bool IsPipeliningPossible(const struct SessionHandle *handle,
+                                 const struct connectdata *conn)
 {
-  if(handle->multi && Curl_multi_canPipeline(handle->multi) &&
-      (handle->set.httpreq == HTTPREQ_GET ||
-       handle->set.httpreq == HTTPREQ_HEAD) &&
-      handle->set.httpversion != CURL_HTTP_VERSION_1_0)
+  if((conn->handler->protocol & PROT_HTTP) &&
+     handle->multi && Curl_multi_canPipeline(handle->multi) &&
+     (handle->set.httpreq == HTTPREQ_GET ||
+      handle->set.httpreq == HTTPREQ_HEAD) &&
+     handle->set.httpversion != CURL_HTTP_VERSION_1_0)
     return TRUE;
 
   return FALSE;
@@ -2760,13 +2762,6 @@ bool Curl_isPipeliningEnabled(const struct SessionHandle *handle)
 CURLcode Curl_addHandleToPipeline(struct SessionHandle *data,
                                   struct curl_llist *pipeline)
 {
-#ifdef DEBUGBUILD
-  if(!IsPipeliningPossible(data)) {
-    /* when not pipelined, there MUST be no handle in the list already */
-    if(pipeline->head)
-      infof(data, "PIPE when no PIPE supposed!\n");
-  }
-#endif
   if(!Curl_llist_insert_next(pipeline, pipeline->tail, data))
     return CURLE_OUT_OF_MEMORY;
   return CURLE_OK;
@@ -2876,7 +2871,7 @@ ConnectionExists(struct SessionHandle *data,
 {
   long i;
   struct connectdata *check;
-  bool canPipeline = IsPipeliningPossible(data);
+  bool canPipeline = IsPipeliningPossible(data, needle);
 
   for(i=0; i< data->state.connc->num; i++) {
     bool match = FALSE;
@@ -2928,11 +2923,11 @@ ConnectionExists(struct SessionHandle *data,
       struct SessionHandle* sh = gethandleathead(check->send_pipe);
       struct SessionHandle* rh = gethandleathead(check->recv_pipe);
       if(sh) {
-        if(!IsPipeliningPossible(sh))
+        if(!IsPipeliningPossible(sh, check))
           continue;
       }
       else if(rh) {
-        if(!IsPipeliningPossible(rh))
+        if(!IsPipeliningPossible(rh, check))
           continue;
       }