Bug#924792: pidof: unsanitized user input makes pidof crash

[Jesse Smith]

This is a good find and I see two fairly straight forward ways to deal
with the bug:

1. We can drop the new -f flag. This is a little inconvenient for some
users, but immediately plugs the hole.

2. We can write our own print function that will not crash or give weird
behaviour the way printf() does. Right now I'm leaning toward the latter
option. It's a little more work, but probably a nicer fix for everyone
in the long run.

- Jesse