/*D
   MPI_T_category_changed - Get the timestamp indicating the last change to the categories

Synopsis:
.vb
int MPI_T_category_changed(int *update_number)
.ve

Output Parameters:
. update_number - update number (integer)

Notes:
If two subsequent calls to this routine return the same timestamp, it is guaranteed that
the category information has not changed between the two calls. If the timestamp retrieved
from the second call is higher, then some categories have been added or expanded.

.N ThreadSafe

.N Errors
.N MPI_SUCCESS
.N MPI_T_ERR_INVALID
.N MPI_T_ERR_NOT_INITIALIZED
.N MPI_ERR_OTHER

D*/

