Revert "core, plugins: replace "%lx" by "%p" in calls to sscanf"

This reverts commit e64ab3c675.

This was causing incorrect conversion of strings "0x..." to pointers on systems
like Solaris/illumos.

And as a side effect, buffers were sometimes empty in weechat relay clients
like glowing-bear.

src/plugins/script/script-mouse.c

@@ -41,6 +41,7 @@ script_mouse_focus_chat_cb (const void *pointer, void *data,
 {
     const char *buffer;
     int rc;
+    unsigned long value;
     struct t_gui_buffer *ptr_buffer;
     long x;
     char *error, str_date[64];
@@ -58,10 +59,12 @@ script_mouse_focus_chat_cb (const void *pointer, void *data,
     if (!buffer)
         return info;
 
-    rc = sscanf (buffer, "%p", &ptr_buffer);
+    rc = sscanf (buffer, "%lx", &value);
     if ((rc == EOF) || (rc == 0))
         return info;
 
+    ptr_buffer = (struct t_gui_buffer *)value;
+
     if (!ptr_buffer || (ptr_buffer != script_buffer))
         return info;