Small fixes

I ran a static analyser on fcgiwrap and found some issues. However, after some time I gave up. fcgiwrap ignores return values or improperly handles errors, that I would say it's more more to fix this than to reimplement fcgiwrap (perhaps in a language other than C). Moreover, libfcgi looks broken (see 9e8bab9).

Perhaps some of the changes are still useful.