Applied patches provided Loïc Dachary, adding regex used to
error message when parser is unable to parse a line as
well as resetting the field name list, potentially allowing
the same object to be used to be reinitialized from a new
format.
See:
http://code.google.com/p/apachelog/issues/detail?id=1
http://code.google.com/p/apachelog/issues/detail?id=2