In mpiuni, define some types needed by PIO when _NETCDF4 is defined

mpiuni builds on perlmutter were failing; this should fix the issue.

src/Infrastructure/stubs/mpiuni/mpi.h

@@ -136,8 +136,11 @@ extern int MPIUNI_Memcpy(void*,const void*,int,enum CheckForMPIInPlace_Flag);
 #define MPI_UNSIGNED        sizeof(unsigned int)
 #define MPI_LOGICAL         sizeof(int)
 #define MPI_LONG            sizeof(long)
+#define MPI_LONG_LONG       sizeof(long long)
 #define MPI_LONG_LONG_INT   sizeof(long long int)
+#define MPI_UNSIGNED_LONG_LONG sizeof(unsigned long long)
 #define MPI_SHORT           sizeof(short)
+#define MPI_UNSIGNED_SHORT  sizeof(unsigned short)
 #define MPI_UB              sizeof(long)
 #define MPI_FLOAT_INT       (sizeof(float)+sizeof(int))
 #define MPI_DOUBLE_INT      (sizeof(double)+sizeof(int))