A C++ shibboleth?

As far as I am aware (health warning, I'm no C++ expert) the following syntax is only ever used in C++:

```
#include <cstdint>
```

Searching .com for this string returns [overwhelmingly C++ results](https://github.com/search?l=c&q=%23include+%3Ccstdint%3E&ref=simplesearch&type=Code) and all of the 'C' results were actually mis-classifications by linguist already.

Those more obscure results would presumably be picked up in language.rb [here](https://github.com/github/linguist/blob/master/lib/linguist/language.rb#L118)?

Could do with a few more :eyes: on this to check I'm not making this stuff up.