reshuffle API so that ContainerFD::getattr can pass its index down
into Container::getattr() to get the file size.
continue to purge out index stuff from container class (need to move
IndexFileInfo and related functions out).

Container::collectContents() stays in container as a helper function.

add in more indexing code to ByteRangeIndex, including HostEntry,
ContainerEntry, and ChunkFile.

flesh out more of the other byte range functions too.
move in the HostEntry/ContainerEntry handling code, but break
it out into files (BRI_*.cpp).   The data structures for the
main ByteRangeIndex object are defined.  The BRI_Insert isn't
complete yet (finishing the overlap handler), but checkpoint
work in progress.
finish insert code restructure
add +ContainerEntry::older_than() to allow for for tie breaking
when timestamps match.

don't back up "prev" in a map if it is already at map.begin()
(behavior not defined in C++, best not to do it).

if we have an overlap and the entry we are trying to insert
is size 0, then we can just discard it rather than trying to
run it through the overlap handler.

fix minor error in setting "first" in the overlap handler.
add the parallel indexer reader framework (in BRI_Reader.cpp).
fix bug in BRI_Merge where merge_idx() wasn't updating the chunk_id.

(XXX: chunk_id may not be necessary, sine we can always use the
size() of the vector).
finish BRI_Populate, start BRI_Global.
add populate functions
add global_from_stream()
pull in the rest of the global routines.
clarify where global_to_stream is coming from
rework EOF and size tracking to be in the index instead of having
the container do it.
add query code
add some comments on query
add in code for index_add (write side add index record),
and also handle index_sync() as well, since index_add needs it too.
add code for index_open.   compiles, but I need to review the
BRI locking protocol.  e.g. should global_from_stream be locking
the BRI?
clean up the locking for the ByteRangeIndex and update locking
related commments.
add in calls to pthread_mutex_destroy
checkpoint index_close progress, need to revise handling of eof/byte
count and how it works with the meta files managed by ContainerFD.
revise index_close API to return metainfo for creating metadroppings
at file close time.  currently only used for writeable file handles.