Description:
    Remove all traces of MPI-POSIX VFD and GPFS detection/code.

    Remove remaining traces of stream VFD.

    Remove testpar/t_posix_compliant test (it's not actually verifying anything).

    Clean up H5D__mpio_opt_possible() further.

    Moved environment variable that disables MPI collective operations into
MPI-IO VFD (instead of it being in src/H5S.c).

    A few other small code cleanups.

Tested on:
    Mac OSX/64 10.9.2 (amazon) w/parallel & serial


git-svn-id: https://svn.hdfgroup.uiuc.edu/hdf5/trunk@24864 dab4d1a6-ed17-0410-a064-d1ae371a2980