implement lua_thread_abort, add lua_thread_yield_state func, and fix lua_thread_resume_state to use protected mode

accept NULL for log function fmt arg

merge lua-threads branch, all lua_console input is now executed in a new lua thread

fix lua_nexus_sleep to use EV_TIMEOUT + misc

fix console to ignore input while waiting, and rename have_input -> have_prompt

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