Add include guards and make public a few routines that add values
to the hash.
Two part patch:

First: refactor out the emission of entries into the .debug_loc section
into its own routine.

Second: add a new class ByteStreamer that can be used to either emit
using an AsmPrinter or hash using DIEHash the series of bytes that
would be emitted. Use this in all of the location emission routines
for the .debug_loc section.

No functional change intended outside of a few additional comments
in verbose assembly.