fix #230 making the module compatible with nginx versions older than 1.7.3 again

src/ngx_http_push_stream_module_utils.c

@@ -313,10 +313,11 @@ ngx_http_push_stream_convert_char_to_msg_on_shared(ngx_http_push_stream_main_con
         return NULL;
     }
 
-    if ((msg->formatted_messages = ngx_slab_calloc(shpool, sizeof(ngx_str_t) * msg->qtd_templates)) == NULL) {
+    if ((msg->formatted_messages = ngx_slab_alloc(shpool, sizeof(ngx_str_t) * msg->qtd_templates)) == NULL) {
         ngx_http_push_stream_free_message_memory(shpool, msg);
         return NULL;
     }
+    ngx_memzero(msg->formatted_messages, sizeof(ngx_str_t) * msg->qtd_templates);
 
     for (q = ngx_queue_head(&mcf->msg_templates); q != ngx_queue_sentinel(&mcf->msg_templates); q = ngx_queue_next(q)) {
         ngx_http_push_stream_template_t *cur = ngx_queue_data(q, ngx_http_push_stream_template_t, queue);