fopen() kills stdin

[githubaf]

fopen() kills stdin.
The bug has been fixed in https://github.com/bebbo/libnix/blob/master/sources/nix/stdio/fopen.c
Please review/take over the change if possible.

I just copied his fopen.c into your libnix-tree and recompiled/installed it. Works, error is gone.

Here is a test-file that demonstates the bug:

fopen_test.tar.gz

[sezero]

Created #3 for this