* core.c (core_open, core_close, core_xfer_memory): Move

    * core.c (core_open, core_close, core_xfer_memory):  Move
        section table pointers and bfd* into the target_ops.
        (core_open):  Allow errors in shared lib reading, etc.
        (core_files_info):  Describe shared library sections.

        * exec.c (exec_open, exec_close, exec_xfer_memory, xfer_memory,
        exec_files_info, set_section_command):  Move section table
        pointers and bfd* into the target_ops.
        (add_to_section_table):  Add BFD to section table.

        * target.c (target_xfer_memory, target_info):  Pass target to
        xfer_memory and target_info functions.
        * target.h:   ''

        * gdbcore.h:  Move struct section_table.
        * target.h:  New home of struct section_table.