fix loading of libraries.

When loading external libraries I was getting this kind of errors:
> enable
load_scripts (exec):
error loading module 'socket.core' from file '/usr/lib/x86_64-linux-gnu/lua/5.1/socket/core.so':
        /usr/lib/x86_64-linux-gnu/lua/5.1/socket/core.so: undefined symbol: lua_gettop
Error: Plugin clish_plugin_lua.so init retcode: -1