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/plugin-script.c

@@ -407,7 +407,7 @@ plugin_script_str2ptr (struct t_weechat_plugin *weechat_plugin,
                        const char *script_name, const char *function_name,
                        const char *str_pointer)
 {
-    void *pointer;
+    unsigned long value;
     int rc;
     struct t_gui_buffer *ptr_buffer;
 
@@ -417,9 +417,9 @@ plugin_script_str2ptr (struct t_weechat_plugin *weechat_plugin,
     if ((str_pointer[0] != '0') || (str_pointer[1] != 'x'))
         goto invalid;
 
-    rc = sscanf (str_pointer, "%p", &pointer);
+    rc = sscanf (str_pointer + 2, "%lx", &value);
     if ((rc != EOF) && (rc >= 1))
-        return pointer;
+        return (void *)value;
 
 invalid:
     if ((weechat_plugin->debug >= 1) && script_name && function_name)