Some cleanup

To simplify life with ttfautohint and reduce file-size (marginally):
- mixed glyphs with a referenced component are changed to reference all
componenents or none and overlaps are removed
- remove some backgrounds
- remove unneeded/experimental glyphs
- remove Egrave.sups/subs/ordn/sinf
- for some modifier glyphs add references to corresponding combining
acc.
- remove a last stray anchor in a spacing modifier