Significant improvement in fetch time for item clearances. On large
boards with lots of nets, maybe 10% faster zone fills and about
2x speedup on track-to-track DRC.
It's a bit of a hack because they're statically initialized and
so we can't make use of the _() macro. We do still want it in the
code, however, because the string harvesting is based off of it.
Fixes: lp:1833000
* https://bugs.launchpad.net/kicad/+bug/1833000