Mostly this just changes ` to ' in static text. Some exceptions:
* INSTALL.REPO: Use curved quotes, as the diagnostic in question
typically does that now.
* admin/quick-install-emacs (TRY, top level):
Use straight quoting in diagnostics.
* src/README: Fix working-directory confusion.
This is in preparation for generating the former automatically
from the latter.
* admin/notes/bugtracker, admin/notes/copyright, admin/notes/newfile:
ChangeLog -> change log
* admin/notes/changelogs: Remove, merging old contents to ...
* admin/notes/repo: ... here.
* doc/emacs/maintaining.texi (Change Log): Mention that ChangeLog files may
be copied to or from a version control system.
* doc/emacs/trouble.texi (Sending Patches): Point to the commit messages.
* doc/lispref/intro.texi (Acknowledgments): ChangeLog file -> change log entries.
* doc/lispref/tips.texi (Library Headers): Emacs uses a version control system.
* etc/CONTRIBUTE: Give advice about git commit messages and how
to generate proposed patches containing them.
