Streamline punctuation of log messages

Make sure that all log messages end with a correct punctuation mark.

The rules for formatting log messages are:

 1. Add punctuation marks to all messages passed to the actual logging
    functions like Log() and LogDebug().
 2. Don't add any punctuation marks to messages that are stored in
    variables for later use or are passed over the network.
 3. IP addresses, DNS host names and IRC server names should be quoted.
 4. Messages originating in the network should be quoted (at least if
    they are "untrusted" or variable).

Most probably this patch doesn't fix all mistakes, but it should be a
good starting point ...