No syntax highlighting in included c_cpp files

Hello,

I'll be honest. I don't know what information you need. I am using the code, like so:

```
[import:1-, unindent:"true", lang="c_cpp"](code/c/example.c)
```
There is no syntax highlighting in this case, but when using the exact same importing scheme and another language, it works fine, for example:

```
[import:1-, unindent:"true", lang="csharp"](code/c/example.cs)
```

I have tried both `c` and `cpp` for `.c` and `.cpp` files respectively, but these do not seem to work. I fear I might be missing something in the documentation, but I don't know where to look. Could someone point me in the right direction to solve this issue?

Note that this is with the default settings. Ace will not work for our purposes because it doesn't seem to work with the theme-api. That is, when changing our theme, we should also change the language we are reading in from a file somewhere. When doing this with ace, only the initial language is displayed. When changing the language, no codeblock appears.

If I understand correctly, c/c++ syntax highlighting was fixed for ace (but not for default) in issue #21?

デフォルト設定で2つのインポート例を再現し、言語パス c_cpp、c、cpp、csharp を比較します。issue #21 が関連する参照です。デフォルト構成で含まれている C および C++ ファイルにシンタックスハイライトが適用され、テーマの変更も引き続き機能すれば完了です。

索引モデルが issue の本文から書いたものです。