Pick up ignore files from daemons started later

[akerbos]

We already read ignore files from other ltx2any daemons which already exist at startup. Already running daemons, however, don't update themselves with new ignore files, causing the older process to trigger rebuilds whenever the newer one rebuilds.

This is only a problem if two daemons run in the same directory, but still.

I see two options:

1. Create a second listen instance that watches for ignore files and updates the main listener as necessary.
2. Check for new ignore files before a re-run.

The second seems simpler and sufficient.

Note: What about a daemon that runs in a subfolder of another project? It won't pick up any dynamic file changes from the "outer" daemon, obviously, but the outer one can't find the inner one's ignore file. Should we watch for such or just have users which such setups deal with it?

[akerbos]

Should not $ignfilelistener do exactly that? Check!

[akerbos]

This seems indeed to have been implemented for ages. Duh.