setlocale: Enable replacement on Cygwin 1.5. * m4/setlocale.m4 (gl_FUNC_SETLOCALE): Set REPLACE_SETLOCALE also on Cygwin 1.5.x. * doc/posix-functions/setlocale.texi: Mention that the problem with the LC_CTYPE category also exists on Cygwin 1.5.x.