hdf5_msb

Add all extant virtual files to a list.  Add an "exclusive owner" (`exc_owner`)
member to all virtual files.  Add a routine, H5FD_has_conflict(), that returns
true if a new virtual file is identical to an existing virtual file that has an
exclusive owner.  Establish an exclusive owner for a VFD SWMR virtual file's
lower virtual file.

Rename bsdqueue.h to H5queue.h and install it, since it's used by H5FDpublic.h.

This is part of a changeset that helps us avoid creating multiple H5F_shared_t
for one file when virtual datasets are used with VFD SWMR.  The old code for
deduplicating VFD SWMR H5F_shared_t instances did not work correctly with VFD
SWMR, so we'd end up with multiple H5F_shared_t all active on the same file.