Creates a new ScannerOptions struct with sensible defaults.

Creates a new Scanner instance using |client| to talk to the log, and taking configuration options from |opts|.

TODO(alcutter): this signature is syntactically correct, but invalid.

MatchAll is a Matcher which will match every possible Certificate and Precertificate.

MatchNone is a Matcher which will never match any Certificate or Precertificate.

MatchSubjectRegex is a Matcher which will use |CertificateSubjectRegex| and |PrecertificateSubjectRegex| to determine whether Certificates and Precertificates are interesting.

Scanner is a tool to scan all the entries in a CT Log.

ScannerOptions holds configuration options for the Scanner.

Clients wishing to implement their own Matchers should implement this interface:.