Issue #2713831 by vegantriathlete, lisa.ugray, joshi.rohit100, jhodgdon, deviantintegral, kellyimagined, alexpott, akalata, soulsesa: Document #machine_name exists parameters

Issue #2722265 by willito, kellyimagined, joachim, hussainweb, munizjor, selfuntitled, lisa.ugray, soulsesa, The Sean, kjl16, kurthill4: docs for MailManager::mail() refer to obsolete function user_preferred_langcode()