incorrect usage of url() in module

the graphviz_formats.module file still uses the url() function in the 5.x style syntax.

Changing the two lines that use url to this:

$outurl = url($outpath, array('absolute' => TRUE));
$modurl = url(drupal_get_path('module', 'graphviz_formats'), array('absolute' => TRUE));

corrected the issue for me.