Summary
- added glyph from "Deja Vu Sans Mono" font;
- tuned messages;
- merged
- allow TeX comment % in formal comment body, but avoid extra space (cf. d7c6054b2ab1);
- tuned;
- tuned;
- more general error suffixes, e.g. for messages that are broken over several lines;
- another Latex error seen in the wild: Undefined control sequence. \isamarkupcancel #1->\xout
- clarified default;
- clarified formal comments;
- prefer formal comments;
- added \<^cancel> operator for unused text;
- tuned;
- restored naming of lemmas after corresponding constants