vchoi_fork

Take a stab at a "zoo" writer for VFD SWMR: write all of the same
objects as the cache_image test does.  The zoo writer is a work in
progress.

This version is useful as a reproducer for the hang in the global heap
that I stumbled over, yesterday.  I run this to reproduce,

env HLOG="pbio=on" ./vfd_swmr_zoo_writer -W -a