Generate the tables in InstrUtils.c...almost.

This patch adds code to opcode-gen to generate the opcode info tables
currently built at vm start time, but they are left commented out for
now. I wanted to separate the work of getting these tables generated
from the work of getting those new tables hooked up, and this seemed
like a reasonable way to cut through the larger effort.

To be clear, I've already verified that the data in the new
pregenerated tables matches what's in the status quo.

Change-Id: Ie73dc6c6a5721e8f714f845c97b5338141995770