clarified how/when to use client or guessed mime-types and extensions on a File instance (closes #5039)
[HttpFoundation] added some more phpdocs to clarify usage
[HttpFoundation] added a way to inject a custom magic file into FileinfoMimeTypeGuesser (closes #6963)
[HttpFoundation] fixed phpdoc
[HttpFoundation] updated the list of known mime types (sync from Apache)