Very basic file-analyzer for x509 certificates. Mostly ripped from
the ssl-analyzer and the topic/bernhard/x509 branch.

Simply prints information about the encountered certificates (I have
not yet my mind up, what I will log...).

Next step: extensions...
parse out extension. One event for general extensions (just returns the
openssl-parsed string-value), one event for basicconstraints (is a certificate
a CA or not) and one event for subject-alternative-names (only DNS parts).
rip out x509 code from ssl analyzer. Note that since at the moment
the file analyzer does not yet re-populate the info record that
means quite a lot of information is simply not available.
Make x509 certificates an opaque type
Merge remote-tracking branch 'origin/master' into topic/bernhard/file-analysis-x509

Conflicts:
	src/analyzer/protocol/ssl/events.bif

Still broken.
Merge remote-tracking branch 'origin/master' into topic/bernhard/file-analysis-x509

Conflicts:
	src/analyzer/protocol/ssl/events.bif
	src/analyzer/protocol/ssl/ssl-analyzer.pac
Backport crash fix that made it into master with the x509_extension
backport from here.
Second try on the event interface.

Now the x509 opaque is wrapped in the certificate structure. After
pondering on it for a bit, this might not be the brightest idea.
Add verify functionality, including the ability to get the validated
chain. This means that it is now possible to get information about the
root-certificates that were used to secure a connection.

Intermediate commit before changing the script interface again.

addresses BIT-953, BIT-760
X509 file analyzer nearly done. Verification and most other policy scripts
work fine now.

Todo:
 * update all baselines
 * fix the circular reference to the fa_file structure I introduced :)
   Sadly this does not seem to be entirely straightforward.

addresses BIT-953, BIT-760
Fix circular reference problem and a few other small things.

SSL::Info now holds a reference to Files::Info instead of the
fa_files record.

Everything should work now, if everyone thinks that the interface is
ok I will update the test baselines in a bit.

addresses BIT-953, BIT-760
Replace libmagic w/ Bro signatures for file MIME type identification.

Notable changes:

- libmagic is no longer used at all.  All MIME type detection is
  done through new Bro signatures, and there's no longer a means to get
  verbose file type descriptions (e.g. "PNG image data, 1435 x 170").
  The majority of the default file magic signatures are derived
  from the default magic database of libmagic ~5.17.

- File magic signatures consist of two new constructs in the
  signature rule parsing grammar: "file-magic" gives a regular
  expression to match against, and "file-mime" gives the MIME type
  string of content that matches the magic and an optional strength
  value for the match.

- Modified signature/rule syntax for identifiers: they can no longer
  start with a '-', which made for ambiguous syntax when doing negative
  strength values in "file-mime".  Also brought syntax for Bro script
  identifiers in line with reality (they can't start with numbers or
  include '-' at all).

- A new Built-In Function, "file_magic", can be used to get all
  file magic matches and their corresponding strength against a given
  chunk of data

- The second parameter of the "identify_data" Built-In Function
  can no longer be used to get verbose file type descriptions, though it
  can still be used to get the strongest matching file magic signature.

- The "file_transferred" event's "descr" parameter no longer
  contains verbose file type descriptions.

- The BROMAGIC environment variable no longer changes any behavior
  in Bro as magic databases are no longer used/installed.

- Reverted back to minimum requirement of CMake 2.6.3 from 2.8.0
  (it's back to being the same requirement as the Bro v2.2 release).
  The bump was to accomodate building libmagic as an external project,
  which is no longer needed.

Addresses BIT-1143.
Merge branch 'master' into topic/jsiwek/file-signatures
Refactor common MIME magic matching code.

Put some methods in file_analysis::Manager that can perform the
matching process and return MIME type results.  Also helps to
centralize the management/re-use of a signature matcher object.
Various minor changes related to file mime type detection.

- Improve or just remove some file magic signatures ported from libmagic
  that were too general and matched incorrectly too often.

- Fix MHR script's use of fa_file$mime_type before checking if it's
  initialized.  It may be uninitialized if no signatures match.

- The "fa_file" record now contains a "mime_types" field that contains
  all magic signatures that matched the file content (where the
  "mime_type" field is just a shortcut for the strongest match).
Improve performance of MHR script, addresses BIT-1139.

The MHR script involves a "when" statement which can be expensive due to
the way it clones frames/vals.  In this case, the fa_file record is
expensive to clone, but this change works around that by unrolling only
the necessary fields from it that are needed to populate a Notice::Info
record.  A drawback to this is that the full fa_file or connection
records aren't available in the Notice::Info record when evaluating
Notice::policy hooks for MHR hit notices (though they can possibly be
recovered by using e.g. the lookup_connection() builtin_function).
Change x509 log - now certificates are only logged once per hour.

Add parsing of several more types to SAN extension.

Make error messages of x509 file analyzer more useful.

Fix file ID generation.

You apparently have to be very careful which EndOfFile function of
the file analysis framework you call... otherwhise it might try
to close another file id. This took me quite a while to find.

addresses BIT-953, BIT-760, BIT-1150
Merge remote-tracking branch 'origin/master' into topic/bernhard/file-analysis-x509
Revert change to only log certificates once per hour.

addresses BIT-953, BIT-760, BIT-1150
Finishing touches of the x509 file analyzer.

Mostly baseline updates and new tests.

addresses BIT-953, BIT-760, BIT-1150