extern "C" functions are ignored

[zhuoqiang]

• version: 0.5

The function doc will be ignored in case an extern "C" prefix in its declaration:

Input: example.h

/// Foo doc
extern "C" void Foo();

/// Bar doc
void Bar();

the output:

# Header file `example.h`

``` cpp
extern "C" 
void Bar();
```

## Function `Bar`

``` cpp
void Bar();
```

Bar doc

-----

the Foo() doc is missing. removing extern "C" get us Foo() doc back:

the expected:

# Header file `example.h`

``` cpp
void Foo();

void Bar();
```

## Function `Foo`

``` cpp
void Foo();
```

Foo doc

-----

## Function `Bar`

``` cpp
void Bar();
```

Bar doc

-----