res_pjsip: Add 'user_eq_phone' option to add a 'user=phone' parameter when applicable.

This change adds a configuration option which adds a 'user=phone' parameter if the user
portion of the request URI or the From URI is determined to be a number.

Review: https://reviewboard.asterisk.org/r/4073/


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@425804 f38db490-d61c-443f-a65b-d21fe96a405b