polymodel code now has basic class management in place and no longer uses memset

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9833 387891d4-d844-0410-90c0-e4c51a9137d3
turn hud_anim back into an actual struct

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9834 387891d4-d844-0410-90c0-e4c51a9137d3