CommanderDJ's patch for Mantis #2899 (AddressSanitizer: heap-buffer-overflow in snd_play() sound.cpp)

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@11083 387891d4-d844-0410-90c0-e4c51a9137d3
fix Mantis #2987 (AddressSanitizer: global-buffer-overflow in message_queue_process())

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@11084 387891d4-d844-0410-90c0-e4c51a9137d3