Reverse Lua-language bridging
The common way of deployin built-in Lua: FROM application -> TO a
lua_State. Both directions can iow be done. The reversed bridging in
mycalc is achieved by lending an existing (created but inactive)
lua_State, the service VM (if started).
Methods for invoking:
* pcall - using "During" protocol: '\l<string>'
* interactive - Ener using the "service" command (new). Exit using
^D