Recognize the *-*-windows* config triplets introduced on 2023-06-26.
* gettext-runtime/configure.ac: Treat windows* as equivalent to mingw*.
* gettext-runtime/intl/configure.ac: Likewise.
* gettext-runtime/libasprintf/configure.ac: Likewise.
* gettext-tools/configure.ac: Likewise.
* gettext-tools/m4/locale-de.m4 (gt_LOCALE_DE_UTF8): Likewise.
* libtextstyle/configure.ac: Likewise.
* m4/woe32-dll.m4 (gl_WOE32_DLL): Likewise.
