Bring H5DOappend(), H5P[s|g]et_object_flush_cb, and H5P[s|g]et_append_flush
from revise_chunks branch to trunk. Brings along updated metadata cache
entry tagging, and the internal object flush routine.
Tested on:
MacOSX/64 10.11.4 (amazon) w/serial, parallel & production
(h5committest forthcoming)