webirc: Check validity of given IP.
startup: Check return value of open /dev/null. Don't fclose stdin/stdout/stderr.

Open /dev/null for standard fds earlier, so a failure can be reported.
Do not fclose stdin/stdout/stderr but just overwrite the fds with
/dev/null.
extensions/roleplay: Fix memory leak on every use.
bantool: Close .conf files when done reading.

Not very many files are read, so leaving them open is not a major issue.