localcharset tests: Test in the UTF-8 environment on native Windows.
* m4/windows-rc.m4: New file.
* tests/test-localcharset-w32utf8.sh: New file.
* tests/test-localcharset-w32utf8.c: New file.
* tests/windows-utf8.rc: New file.
* tests/windows-utf8.manifest: New file.
* modules/localcharset-tests (Files): Add these files.
(Depends-on): Add test-xfail.
(configure.ac): Invoke gl_WINDOWS_RC.
(Makefile.am): Arrange to compile test-localcharset-w32utf8 and run
test-localcharset-w32utf8.sh.