Delete unused or undefined functions.

Delete unused or undefined functions.

        * breakpoint.c (ep_parse_optional_filename): Delete.
        * dcache.c (dcache_write_line): Remove declaration.
        * infrun.c (build_infrun): Remove declaration.
        * tracepoint.c (tracepoint_save_command): Remove declaration.
        * linux-nat.c (init_lwp_list): Delete. No longer used.
        * event-loop.c (check_async_signal_handlers): Delete declaration.
        * infrun.c (init_execution_control_state): Delete.
        (proceed): Update comment to avoid mentioning
        init_execution_control_state.
        * target.c (kill_or_be_killed, nosupport_runtime): Delete.
        * ada-lang.c (ada_to_static_fixed_value): Delete.
        * scm-lang.c (evaluate_subexp_scm): Delete declaration.
        * cp-namespace.c (cp_copy_usings): Delete.
        * xml-syscall.c (xml_number_of_syscalls): Delete.
        * progspace.c (find_program_space_by_num): Delete.
        * inflow.c (handle_sigio): Delete declaration.
        * hppa-tdep.c (hppa_alignof): Delete.
        * mipsnbsd-tdep.c (mipsnbsd_sigtramp_offset)
        (mipsnbsd_core_osabi_sniffer): Delete.