int error = InitLibrary(lua_State *L);
lua_Statehas been setup correctly. For example, a plugin might want to setup some metatables or push additional helper tables into the stack. It's impossible to do such things in InitPlugin() since the
lua_Stateisn't ready yet at InitPlugin() call time. That's why this function is available. Many plugins, however, probably don't need to do anything here at all.
InitLibrary() has to return an error code or 0 for success.