`NC` files are being incorrectly identified as `nesC`

Files posted by CAM software, `NC` files are being incorrectly identified as `nesC` files in my repo.

### URL of the affected repository:
https://github.com/kevinkhill/ncstat

### Last modified on:
2020-11-27

### Expected language:
`NC`? gcode? nc? I'm not sure what you want to call it

### Detected language:
`nesC`

Start by reproducing the detection result with the affected repository, https://github.com/kevinkhill/ncstat, and inspect how Linguist distinguishes `.nc` files from nesC. Done means CAM-generated NC files are no longer reported as nesC, with the expected language label clarified.

Written by the indexing model from the issue text.