A set of file analysis extensions.

- Enable manager to associate analyzers with a MIME type. With that,
  one can now say enable all analyzers for, e.g., "image/gif". This is
  exposed to script-land as

    Files::add_analyzers_for_mime_type(f: fa_file, mtype: string)

  For MIME types identified via libmagic, this happens automatically
  (via the file_new() handler in files/main.bro).

- Extend the analyzer API to better match that of protocol analyzers:

    - Adding unique analyzer IDs so that we can refer to instances
      from script-land.

    - Adding subtypes to Components so that a single analyzer
      implementation can support different types of analyzers
      internally.

    - Add an analyzer method SetTag() that allows to set the tag after
      construction.

    - Adding Init() and Done() methods for consistency with what other
      classes offer.

- Add debug logging to the file_analysis stream.

TODO: test cases missing for the new script-land functionality.

scripts/base/init-bare.bro

@@ -60,6 +60,13 @@ type addr_vec: vector of addr;
 ##    directly and then remove this alias.
 type table_string_of_string: table[string] of string;
 
+## A set of file analyzer tags.
+##
+## .. todo:: We need this type definition only for declaring builtin functions
+##    via ``bifcl``. We should extend ``bifcl`` to understand composite types
+##    directly and then remove this alias.
+type files_tag_set: set[Files::Tag];
+
 ## A connection's transport-layer protocol. Note that Bro uses the term
 ## "connection" broadly, using flow semantics for ICMP and UDP.
 type transport_proto: enum {