driver = sql::mysql::get_mysql_driver_instance();God, this is awful. They combine the worst of C with the worst of C++: lots::of::namespaces::in:cpp and really_long_underscored_names_in_c
Well, I thought you were thinking of contributing the code back to the community. If not, then by all means go ahead and try it out. Perhaps later you'll show us that it's easy and we'll have to reconsider.
As for the error you're seeing, I'd guess that it's about the library being incomplete or something wrong with it - it does complain inside the library's own header file, so it shouldn't be an issue with how you're using it.
I still think it would be easier to create a plugin that would use the LuaRocks' MySQL binding and when a player connects it would push the permissions from DB to the player. The cPlayer API just might be enough for this, if not, we could always extend it.