* gdbtk-wrapper.h: Add declarations for GDB_get_prev_frame, GDB_get_next_frame,

    * gdbtk-wrapper.h: Add declarations for GDB_get_prev_frame, GDB_get_next_frame,
        GDB_find_relative_frame, GDB_get_current_frame.
        * gdbtk-wrapper.c (GDB_get_prev_frame, wrap_get_prev_frame): New functions.
        (GDB_get_next_frame, wrap_get_next_frame): New functions.
        (GDB_find_relative_frame, wrap_find_relative_frame): New functions.
        (GDB_get_current_frame, wrap_get_current_frame): New functions.

        * gdbtk-hooks.c (gdbtk_add_hooks): Use "specify_exec_file_hook" so
        that our hook is added to the list of hooks run instead of overwriting
        all other hooks.

        * gdbtk-cmds.c (gdb_stack): Wrap all calls to internal functions and
        deal with errors more gracefully.