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.

libmisc/Makefile.am

@@ -55,4 +55,5 @@ libmisc_a_SOURCES = \
 	xgetgrnam.c \
 	xgetgrgid.c \
 	xgetspnam.c \
-	xmalloc.c
+	xmalloc.c \
+	yesno.c