wcsrtombs: Remove support for OSF/1. * m4/wcsrtombs.m4 (gl_WCSRTOMBS_TERMINATION): Remove macro. (gl_FUNC_WCSRTOMBS): Don't invoke it. Don't define WCSRTOMBS_TERMINATION_BUG. (gl_WCSRTOMBS_NULL): Remove cross-compilation guess for OSF/1. * lib/wcsrtombs.c: Ignore WCSRTOMBS_TERMINATION_BUG.