Slightly improve http_download related allocations.

* use `calloc()` to allocate zero-initialized structs.
* order the allocation of members by their declaration.
* order the freeing of members in reverse order.
* move init of `silent` flag in plugin case.
* fix double free of `tmpname` in `aesgcm_file_get()`.
* make some functions static.

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

src/tools/plugin_download.c

@@ -62,9 +62,9 @@ plugin_download_install(void* userdata)
 {
     HTTPDownload* plugin_dl = (HTTPDownload*)userdata;
 
+    /* We need to dup those, because they're free'd inside `http_file_get()` */
     auto_char char* path = strdup(plugin_dl->filename);
     auto_char char* https_url = strdup(plugin_dl->url);
-    plugin_dl->silent = TRUE;
 
     http_file_get(plugin_dl);