avoid using of devel functions if it is not present

I mean for example - fb_user.module line 202

watchdog('fb_user', t("Created new ... %app" . dprint_r(array(...), 1),
array('!username' => theme('username', $user), '%app' => $fb_app->label)));

replace with

watchdog('fb_user', t("Created new ... %app!debug_info",
array('!username' => theme('username', $user),
'!debug_info' => (function_exists('dprint_r') ? dprint_r(array('session_name' => session_name(), 'session_id' => session_id()), 1) : ''),
'%app' => $fb_app->label)));