hook vfprintf only for better reliability

[eadmaster]

As suggested here.

Another approach could be to use PTRACE tricks.

[cehoffman]

That answer relied on the user explicitly using strace or similar to hook all the other functions for us. While it does save a lot of hooking, it is dependent on strace or similar never using a different print function. Also using strace to run something slows execution considerably in the limited experience. Thanks for the link to the discussion.