memset initialized the wrong level of pointer :-/

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@10079 387891d4-d844-0410-90c0-e4c51a9137d3
make man_thruster a POD struct, and initialize maneuvering thrusters in ship_info initialization

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@10080 387891d4-d844-0410-90c0-e4c51a9137d3
this exited_ship constructor is redundant and interferes with the POD-ness of the struct

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@10081 387891d4-d844-0410-90c0-e4c51a9137d3