+ Assume the headers required for C89 freestanding compilers.
+ * addext.c, backupfile.c, fsusage.c, human.c, pathmax.h,
+ rpmatch.c, userspec.c, xreadlink.c, xstrtol.c: Include <limits.h>
+ without checking for HAVE_LIMITS_H.
+ * backupfile.c, fsusage.c, hash.c, human.c, safe-read.c, userspec.c,
+ xstrtol.c (CHAR_BIT) : Don't define, since <limits.h> is guaranteed
+ to do that.
+ * fatal.c: Include <stdarg.h> without checking for __STDC__.
+ * exclude.c: Include <stdbool.h> unconditionally.
+ * tempname.c: Include <stddef.h> unconditionally.
+ * hash.c: Include <limits.h>, since we no longer define CHAR_BIT.
+ * modechange.c, rpmatch.c (NULL): Don't define, since
+ <stddef.h> does that.
+ * quote.c: Dont include <stddef.h> or <sys/types.h>; not needed.
+ * safe-read.c (INT_MAX): Don't define, since <limits.h> does that.
+ * safe-read.c (TYPE_MINIMUM, TYPE_MAXIMUM): Remove; no longer needed.
+ * xstrtol.c: Likewise.
+ * safe-read.c: Remove TYPE_SIGNED; no longer needed.
+ * savedir.c: Include <stddef.h> instead of defining NULL.
+