Fix minor problems found by static checking.

Fix minor problems found by static checking.

* buffer.h (struct buffer_text, struct buffer):
* frame.h (struct frame):
* window.h (struct window):
Avoid 'bool foo : 1;', as it's not portable to pre-C99 compilers,
as described in ../lib/stdbool.in.h.  Use 'unsigned foo : 1;' instead.
* menu.c (syms_of_menu): Define x-popup-dialog, removing a
no-longer-valid use of HAVE_MENUS.
* xdisp.c (propagate_buffer_redisplay): Now static.