/*D
   MPI_Info_get_nthkey - Returns the nth defined key in info

Synopsis:
.vb
int MPI_Info_get_nthkey(MPI_Info info, int n, char *key)
.ve

Input Parameters:
+ info - info object (handle)
- n - key number (integer)

Output Parameters:
. key - key (string)

.N ThreadSafe

.N Fortran

.N Errors
.N MPI_SUCCESS
.N MPI_ERR_ARG
.N MPI_ERR_INFO
.N MPI_ERR_OTHER

D*/

