Inject code to process `#define`?
I'm trying to wrap The Machinery which has versioned headers and uses a lot of defines for generating code.

An example is this:

```c
#define tm_api_registry_api_version TM_VERSION(0, 3, 0)
```

Where:

```c
#define TM_VERSION(major, minor, patch) (TM_LITERAL(tm_version_t){ major, minor, patch }
```

The generated nim file has:
`# const 'tm_api_registry_api_version' has unsupported value 'TM_VERSION(0, 3, 0)`

Ideally I'd like to pass in my own template `TM_VERSION` so `tm_api_registry_api_version` can be declared in my output file correctly like:

```nim
const tm_api_registry_api_version = TM_VERSION(0, 3, 0)
```

I tried adding this to my generator:
```nim
cOverride:
  template TM_VERSION (Major, Minor, Patch): untyped =
    tm_version_t(major: Major, minor: Minor, patch: Patch)
```

But I get an `invalid indentation` error coming from the nimcache, cPlugin, nimterop nim file where `onSymbolOverride` is empty.
Is there a way to do this or can I modify nimterop to allow for this?