Remove deleted breakpoint from TUI display

Remove deleted breakpoint from TUI display

PR tui/24722 points out that deleting a breakpoint does not cause the
"b" to be removed from the breakpoint display.  The issue here was
that the breakpoint still exists at the moment the breakpoint-deleted
observer is notified.  This fixes the problem by specially handling
the case where a breakpoint is being removed.

gdb/ChangeLog
2019-07-17  Tom Tromey  <tom@tromey.com>

	PR tui/24722:
	* tui/tui-winsource.h (tui_update_all_breakpoint_info)
	(tui_update_breakpoint_info): Add "being_deleted" parameter.
	* tui/tui-winsource.c (tui_update_source_window_as_is): Update.
	(tui_update_all_breakpoint_info): Add "being_deleted" parameter.
	(tui_update_breakpoint_info): Likewise.
	* tui/tui-hooks.c (tui_event_create_breakpoint)
	(tui_event_delete_breakpoint, tui_event_modify_breakpoint):
	Update.