vchoi_fork

[svn-r4746] 
Purpose:
	Feature Fix
Description:
	Changed so the "pio_perf" module handles creating and destroying the
	MPI Comm. Worked it so we get the minimum, maximum, and average times
	over a set of iterations.
Solution:
	Lots. Had to pull the MPI Comm code from the "pio_engine" module and
	place it in the "pio_perf" module. Then worked on a way to have all
	processes send their time output to process 0, who collects it and
	gives back the min, max, and avg times for the iterations.
Platforms tested:
	Linux. Doesn't work if you use more than 1 processor...*hrmph*