Overloading std::to_string is undefined behavior

[goldsborough]

Was browsing the codebase and noticed that we are overloading std::to_string for Glow's Type class. Not to be that guy, but this is undefined behavior as per the standard (only allowed to explicitly specialize templates for user-defined types).

Not sure if we care? If we do, we should probably move that to Type::to_string or something.

Source: https://stackoverflow.com/questions/14402990/should-you-overload-swap-in-the-std-namespace

[nadavrot]

This is a good point. Thanks for catching this Peter. We should fix this.