errno-h: Remove support for OSF/1. * lib/errno.in.h: Don't test EMULTIHOP_HIDDEN, ENOLINK_HIDDEN, EOVERFLOW_HIDDEN. * m4/errno_h.m4 (gl_REPLACE_ERRNO_VALUE): Remove macro. (gl_HEADER_ERRNO_H): Don't invoke it. * modules/errno-h (Makefile.am): Don't substitute EMULTIHOP_HIDDEN, EMULTIHOP_VALUE, ENOLINK_HIDDEN, ENOLINK_VALUE, EOVERFLOW_HIDDEN, EOVERFLOW_VALUE.