Provide support for (Ada) task-specific breakpoints.

    Provide support for (Ada) task-specific breakpoints.

        * ada-lang.h (ada_get_task_number): Add declaration.
        (breakpoint_ada_task_match): Delete declaration.
        * ada-tasks.c (ada_get_task_number): Make non-static.
        * breakpoint.h (struct breakpoint): Add field "task".
        * breakpoint.c (print_one_breakpoint_location): Add handling of
        task-specific breakpoints.
        (create_breakpoint, create_breakpoints, find_condition_and_thread):
        New parameter "task".
        (break_command_really): Update calls to find_condition_and_thread
        and create_breakpoints.
        (breakpoint_re_set_one): Update call to find_condition_and_thread.
        Set b->task.