do not use absolute path to fortune

Here is a patch to use the fortune executable which might not be under `/usr/games`.

By using an absolute path, there was no reason to set the `PATH` variable too.

So, using just the executable name with no path, releaved another bug.
There is not need to use `'` (single quotes) around the paths set with `putenv`.
Using single quotes around the paths, makes the the argument be though as a complete path, so the system tries to find executables under `'/usr/bin:/usr/local/bin:/usr/games'` and not under the different paths (it thinks it is one path).

So, all in all this makes the `%f` in the signature usable in systems that do not place the fortune executable under `/usr/games` and fixes the `PATH` variable setting.


Thanks ;)