Use PRTYPE for the type mask

That's what it's called.

Change-Id: I4a2559ca1a9388d1018a3d647cfcded67e276483
More improvements to existing format docs

Change-Id: Iade5666d5cfe3ce83563894a117f5e23293a4c07
Describe hash tables and extended data blocks

Also includes description of the extended name extended data blocks,
and the hash table for looking up based on those names.

Change-Id: I4279a816ce7cde6230812a48db8ccf6ac9830290
Catch up to statements made false by recent changes

Change-Id: I840ecf2b4ac32ad43f2a8a6dabc01f19de307297