I'm pretty sure developer notes were intended to say constants should be upper
case and variables should be lower case, but right now they are ambiguous about
whether to write:

```c++
extern const int SYMBOL;
```

or:

```c++
extern const int g_symbol;
```

First convention above is better than the second convention because it tells
you without having to look anything up that the value of `SYMBOL` won't change
at runtime. Also I haven't seen other c++ projects using the second convention.