Merge Debian's patch 466_fflush-prompt

* libmisc/Makefile.am, lib/prototypes.h, libmisc/yesno.c, src/grpck.c,
	src/pwck.c: move yes_or_no() from grpck/pwck to a separate
	libmisc/yesno.c (with a read_only argument).
	* libmisc/fields.c, libmisc/yesno.c: Make sure stdout is flushed before
	reading the user's answer.

lib/prototypes.h

@@ -194,4 +194,7 @@ extern struct group *xgetgrgid (gid_t);
 /* xgetspnam.c */
 extern struct spwd *xgetspnam(const char *);
 
+/* yesno.c */
+extern int yes_or_no (int read_only);
+
 #endif				/* _PROTOTYPES_H */