Description:
    Introduce "file I/O info" struct, to hold file & dxpl pointers, and start
propagating up through library.

Tested on:
    Mac OSX/64 10.9.2 (amazon) w/C++, FORTRAN & parallel
    (h5committest coming)


git-svn-id: https://svn.hdfgroup.uiuc.edu/hdf5/trunk@25088 dab4d1a6-ed17-0410-a064-d1ae371a2980