Merge pull request #3 from apolukhin/ap/update2

More polishings for the paper:

1. Update date;
2. Fix typo in section "III. Design decisions";
3. Add synopsis to "Header stacktrace" subsection;
4. Add more constexpr for the God of constexpr;
5. Fix typos in comments in header synopsis;
6. Change wording in brief functions descriptions.