Re: Optimization for lower(), upper(), casefold() functions.

One more thing: I observe that headerscheck is now unhappy:

$ src/tools/pginclude/headerscheck
In file included from /tmp/headerscheck.yOpahZ/test.c:2:
./src/include/common/unicode_case_table.h:8598:24: warning: 'casekind_map' defined but not used [-Wunused-variable]
 static const pg_wchar *casekind_map[NCaseKind] =
                        ^~~~~~~~~~~~

It's not apparent to me why that table needs to be in a header
file and not in the sole user .c file?

Also, probably better to make it const:

-static const pg_wchar *casekind_map[NCaseKind] =
+static const pg_wchar * const casekind_map[NCaseKind] =

            regards, tom lane