Note to my future self on phf_map

[maurges]

I'm on an unsuccessful quest to reduce the binary size. Recently I had an idea that the giant map of keyboard keys made a large contribution.

Well, the contribution was 16K. Fairly large, but not bad all in all. I do want to support all keys, so the only thing I could do otherwise is dynamicaly load something, which would bring an even worse overhead, I think.