* signal/signal.h <__USE_BSD || __USE_XOPEN_EXTENDED>: Define
__need_size_t and include stddef.h.
* sysvipc/sys/msg.h: Likewise.
* posix/sched.h: Likewise.
* hurd/hurd/signal.h (__need_size_t): Define.
* CONFORMANCE: ctype.h and wctype.h no longer define size_t,
neither does signal.h in pedantic ISO C namespaces. stdio.h
no longer defines wint_t or wchar_t.