Use MPI_T for perf counters

[j-woz]

From @GoogleCodeExporter on April 22, 2015 19:3

The MPI_T interfaces should allow us to determine the unexpected message queue 
length.  This is useful to understand whether servers are congested.

Original issue reported on code.google.com by tim.g.ar...@gmail.com on 10 Jun 2014 at 12:10

Copied from original issue: j-woz/exm-issues#705