Fix infinite loop in IndexPack

Fix infinite loop in IndexPack

A programming error using the Inflater API led to an infinite
loop within IndexPack, caused by the Inflater returning 0 from
the inflate() method, but it didn't want more input.  This happens
when it has reached the end of the stream, or has reached a spot
asking for an external dictionary.  Such a case is a failure for us,
and we should abort out.

Thanks to Alex for pointing out that we had 3 implementations of
the inflate rountine, which should be consolidated into one and
use a switch to determine where to load data from.

Bug: 317416
Change-Id: I34120482375b687ea36ed9154002d77047e94b1f
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>