[builder] Update glyph name warning regex
[builder] Update glyph name warning regex

Now names which are too long won't yield warnings, because no feature
compiler actually seems to care and long names are commonly used by
Glyphs. Otherwise, the regex is a bit more strict as it doesn't allow
names to start with digits or periods, with the exception of .notdef.

googlefonts/glyphsLib,googlei18n/glyphsLib