fix SPC example

Signed-off-by: Thomas Naughton <naughtont@ornl.gov>

examples/spc_example.c

@@ -54,8 +54,9 @@ int main(int argc, char **argv)
     char name[256], description[256];
 
     /* Counter names to be read by ranks 0 and 1 */
-    char *counter_names[] = {"runtime_spc_OMPI_BYTES_SENT_USER",
-                             "runtime_spc_OMPI_BYTES_RECEIVED_USER" };
+    /* (See also: ompi_spc_counters_t for list) */
+    char *counter_names[] = {"runtime_spc_OMPI_SPC_BYTES_SENT_USER",
+                             "runtime_spc_OMPI_SPC_BYTES_RECEIVED_USER" };
 
     MPI_Init(NULL, NULL);
     MPI_T_init_thread(MPI_THREAD_SINGLE, &provided);