Replace the memory buffer messages in raw video mode

Created originally on Bitbucket by M1ke_M1ke

Was already merged in Bitbucket before import, marked as merged by the import user

Source changeset not longer availableat the time of import. Commit listwill look empty

This modification replaces the memory buffer messages in raw video mode with a movie camera icon and a compact display of record time, speed in MB/second and writing idle time. For pictures see: http://www.magiclantern.fm/forum/index.php?topic=7503.msg83603#msg83603

A small change was made to bitrate.C to disable showing the mvr buffer status. I made the same small change in bitrate-6d.c although was unable to test that not having a 6D.