* bpwin.itb (BpWin::goto_bp): Handle multiple source windows.

	* bpwin.itb (BpWin::goto_bp): Handle multiple source windows.
	* srctextwin.itb (SrcTextWin::get_file): New method.
	(SrcTextWin::set_tag_to_stack): New method.
	* srctextwin.ith (get_file): Declare.
	* srcwin.ith (update_hook_init, window_list, pc_window): New
	common variables.
	(_choose_window, choose_and_update, is_fixed, get_file): Declare.
	* srcwin.itb (SrcWin::_choose_window): New method.
	(SrcWin::choose_and_update): Likewise.
	(SrcWin::_update): Renamed from update.  Now private.  Added `loc'
	argument.
	(SrcWin::get_file): New method.
	(SrcWin::is_fixed): Likewise.
	(SrcWin::constructor): Only add update hook once.  Append this
	object to window list.
	(SrcWin::destructor): Don't add update hook.  Remove this object
	from window list.  Clear pc_window if necessary.
	(SrcWin::get_top): New method.
	(SrcWin::_set_tag_to_stack): New method.
	(SrcWin::choose_and_display): New method.