stepping over fflush

The extension is freezing when I step over a fflush.

example:
``` C
#include

int main(void)
{
printf("hello\n");
fflush(stdout); // works fine
printf("world");
fflush(stdout); // frezes
return 0;
}
```
compile command:
``` bash
gcc -Wall -Wextra -ggdb -o build/fflush-test fflush-test.c
```
It works fine on gdb alone.

## Expected behaviour
It would step to the line `return 0` and not freeze.