fontc must strip hyphens and other invalid characters from postscript names

[anthrotype]

The post table contains PostScript (glyph) names, which are defined by
https://github.com/adobe-type-tools/agl-specification as only allowing the following characters [A-Za-z0-9_.] and must not be longer than 63 characters.

When we do rename glyphs (when --no-production-names flag is not set), we need to do what fontmake (via ufo2ft) does here:

googlefonts/ufo2ft#274
googlefonts/fontmake#455

basically, remove all non PS-valid characters (e.g. hyphens which often Glyphs.app's names contain for script suffixes -cy), truncate to max 64 chars and handle any duplicates that may arise as result of this stripping/truncating.