lualoader: Add ability to intercept cli commands

[kevans]

Summary

If we failed to execute the input line as pure lua, run the command through parse for consistent argument parsing. Pass the parsed arguments through to a global "cli_execute" written in Lua, which is expected to either handle it or pass it back through to interp_builtin_cmd (via loader.command).

[imp]

stand/common/interp_lua.c

149

This seems to have disappeared.

[kevans]

Don't add leaks that weren't there before

[imp]

I'm good either way, but if you keep what you have a quick comment wouldn't be terrible.

stand/lua/loader.lua

42

was thinking this would just be cmd(...) for symmetry, though I suppose it doesn't matter much since the traditional reason for passing argv[0] isn't relevant here.