* 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.
