src/w32.c: Remove unused code and make static many functions.

src/w32.c: Remove unused code and make static many functions.

(g_b_init_get_sid_identifier_authority, GetSidIdentifierAuthority_Proc)
(get_sid_identifier_authority): Remove, not used.
(globals_of_w32): Don't set g_b_init_get_sid_identifier_authority.
(init_winsock): Remove useless assignment.
(open_process_token, get_token_information, lookup_account_sid)
(get_sid_sub_authority, get_sid_sub_authority_count, get_file_security)
(get_security_descriptor_owner, get_security_descriptor_group)
(is_valid_sid, equal_sid, get_length_sid, copy_sid)
(get_native_system_info, get_system_times, init_user_info, crlf_to_lf)
(is_unc_volume, GetCachedVolumeInformation, get_volume_info)
(is_fat_volume, open_unc_volume, read_unc_volume, close_unc_volume)
(unc_volume_file_attributes, convert_from_time_t)
(create_toolhelp32_snapshot, process32_first, process32_next)
(open_thread_token, impersonate_self, revert_to_self)
(get_process_memory_info, get_process_working_set_size)
(global_memory_status, global_memory_status_ex, socket_to_fd)
(shutdown_handler): Make static.