nstrftime, c-nstrftime: Make %h work on native Windows

[Bruno Haible]

On mingw, I see that the %h specifier testing code runs into the assertion
of  ASSERT (n > 0).

This patch adds support for the %h specifier.


2024-05-27  Bruno Haible  <br...@clisp.org>

        nstrftime, c-nstrftime: Make %h work on native Windows.
        * doc/posix-functions/strftime.texi: Mention the %h problem.
        * lib/strftime.c (__strftime_internal): On native Windows, for %h, do a
        %b directive.

diff --git a/doc/posix-functions/strftime.texi 
b/doc/posix-functions/strftime.texi
index 68af3224a4..7cba218a97 100644
--- a/doc/posix-functions/strftime.texi
+++ b/doc/posix-functions/strftime.texi
@@ -25,6 +25,9 @@
 potentially ambiguous numerical output, on some platforms:
 mingw, MSVC.
 @item
+The %h specifier produces empty output on some platforms:
+mingw, MSVC.
+@item
 The %r specifier produces empty output, at least in a French locale,
 on some platforms:
 macOS 12.5, FreeBSD 14.0.
diff --git a/lib/strftime.c b/lib/strftime.c
index 069bab7095..ccfa79daac 100644
--- a/lib/strftime.c
+++ b/lib/strftime.c
@@ -1251,6 +1251,9 @@ __strftime_internal (STREAM_OR_CHAR_T *s, STRFTIME_ARG 
(size_t maxsize)
           cpy (am_len, a_month);
           break;
 #else
+# if defined _WIN32 && !defined __CYGWIN__
+          format_char = L_('b');
+# endif
           goto underlying_strftime;
 #endif