CLEANUP: map/cli: stop using cli.i0/i1 to store the generation numbers

CLEANUP: map/cli: stop using cli.i0/i1 to store the generation numbers

The "show map"/"clear map" code used to rely on the cli's i0/i1 fields
to store the generation numbers to work with. That's particularly dirty
because it's done at places where ctx.map is also manipulated while they
are part of the same union, and the reason why this didn't cause trouble
is because cli.i0/i1 are at offset 216/224 while the map parts end at
204, so luckily there was no overlap.

Let's add these fields to the map context.