Anonymous enums within structs not supported

The `#enum` binding can bind named `enum`s by name, or anonymous `enum`s by referencing one of the values. However, it cannot reference anonymous `enum`s which are defined within a struct (named `enum`s in structs work fine).

If the header file is
```
struct Baz {
enum { FOO = 0 , BAR = 1 } baz;
};
```
then the binding
```
{#enum FOO as FooBar {underscoreToCase} #}
```
fails with
```
Unknown identifier!
Cannot find a definition for `FOO' in the header file.
```

The same binding works if the enum is declared at global scope.