Before this there was no way to prevent the bot to reply to random
channel noise from a temprorary strong link to another distant mesh.
This provides the ability for users in larger meshes to cap the bot
to reply to only messages sent likely from nearby repeaters. This works
well in conjunction with region scoping.
Default value is still 64, to not change behavior on existing installs,
but the example config.ini's all include a suggested start valu of 10.
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