strverscmp: Work around bug in musl libc 1.2.3 and in Cygwin.
Reported by Dmitry Bogatov <KAction@gnu.org> via Simon Josefsson in
<https://lists.gnu.org/archive/html/bug-gnulib/2024-01/msg00002.html>.
* m4/string_h.m4 (gl_STRING_H_DEFAULTS): Initialize REPLACE_STRVERSCMP.
* m4/strverscmp.m4 (gl_FUNC_STRVERSCMP): Test whether strverscmp works
and set REPLACE_STRVERSCMP if not.
* lib/string.in.h (strverscmp): Consider REPLACE_STRVERSCMP.
* modules/strverscmp (Depends-on, configure.ac): Likewise.
* modules/string (Makefile.am): Substitute REPLACE_STRVERSCMP.
* tests/test-strverscmp.c (main): Add test cases suggested by Dmitry
Bogatov and by Simon Josefsson.
* doc/glibc-functions/strverscmp.texi: Mention the musl and Cygwin bug.
Update version info regarding FreeBSD.