[PATCH 0/3] MR3578: freopen() fix.

[eric pouech (＠epo)]

I stumbled onto this while using freopen() for debugging purposes.
Basically, freopen() fails if the FILE has been created with
an invalid handle.

So, this MR contains:
- basic tests for freopen (no issue there, just for coverage purposes)
- tests for freopen on FILE with invalid handle
- fix for freopen