Remove typedef struct in some mdtypes files

Remove typedef struct in some mdtypes files

The idiom

typedef struct { /*...*/ } t_foo;

is a C anachronism we use in some places, that permits the use of
t_foo without struct, but inhibits the use of

struct foo;

forward declarations in all headers that include such structs,
etc.

Removed this so that in future, e.g. the interface of IForceProvider
can use these structs in name, rather than resort to hackery on void
pointers (as we do for force reduction buffers for different reasons).

Regenerated the group-scheme kernels, which all now need to refer to
struct t_forcerec because they compile as C.

Change-Id: I5eb07aa018c54cc74df6dfc918b559e84ea996a8