master
[build]: Add/update .gitignore files.
[doc,man]: Sync with Dave's typo fixes.
[man]: Clean up stray Texinfo syntax.
groff_diff(7): Fix style nit.
groff_font(5): Add "Notes" section.
[doc,man]: Clarify, sync trout/grout format stuff.
[chem,man,gropdf,groff,tmac]: Give man(1) hint.
Declare groff's provenance consistently (redux).
roff(7): Fix content and style nits.