fix lua_console to use new lua_thread API

fix lua_thread to call lua_resume from outside TL state, and to never call the callback directly

implement lua_threads, nexus:sleep test func, and basic support in console/lua_console... doesn't actually work yet

slight tweaks to nexus_lua, use error_t and no need to pop the loaded chunk ourselv - lua_pcall will always do that

implement LUA_ARG_INT

don't keep console SIGINT behaviour after it was destroyed, instead, have nexus handle it like SIGTERM, and have console override that

replace lua_client_networks/lua_network_channels with iterators

implement lua_client_networks and lua_network_channels

use irc_conn_self in irc_chan

implement msg_proto and associated test, fix misc. other bugs (including changing error_info::code to a signed int\!)