Made option_t use SIZE_MAX for max_appearances since it is a size_t.
Made parse_command_line throw a parse_error_t.
Made ifdef WEBRESDIR in command_line.cc be properly indented.
Decoupled get_web_path, get_local_addresses, and get_service_address_ports from command line parsing.
Implemented parse_host_and_port.
Implemented get_io_backend_option.