- Many, many updates to the public header files.
- tidyenum.h was reorganized substantially in order to better generate
documentation with Doxygen.
- This was also a good time to clean up all of the various enums for languages
and strings. Everything is simple and in a single enum now, other than a
couple of cases (TidyOptionId, for example, doesn't need to be redefined).
- A full and complete audit of the strings meant some opportunities to delete
useless strings.
- Reorganized the order of the strings in language_en.h in order to better
find things when programmers want to make changes. There are a lot fewer
internal "sections" now, and everything has been painstakingly sorted within
the remaining sections.
- Consequently rebased all of the PO's, POT, and other language files.
- Updated several of the READMEs with the newest information.
- Made the READMEs easier to copy into the Doxygen project by changing some of
the code format for compatibility, mainly the use of tildes instead of
backslashes for code blocks.
- Added tidyGetMessageCode() to message API. Despite the huge diff, this is the
only externally-visible change, other than removing some enums (but not their
values!).
- Passing `next` tests on Mac, Linux, Win10.
