show-tileset-diffs.pl - Tweaks and debugging

'ALTTILE' added as a display unit.
Failed patches are emitted with headers.
More understandable signifiance detection code.
More reliable significance detection code.
Even more tileset harmonizations.

Grasses, frequencies, glazes, and more.
Merge branch 'harmonize_raws' into unified

* harmonize_raws:
  Even more tileset harmonizations.
  show-tileset-diffs.pl - Tweaks and debugging