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).

src/file_analysis/Manager.h

@@ -285,6 +285,7 @@ public:
 	 */
 	std::string DetectMIME(const u_char* data, uint64 len) const;
 
+
 protected:
 	friend class FileTimer;
 
@@ -370,6 +371,12 @@ private:
 	static string salt; /**< A salt added to file handles before hashing. */
 };
 
+/**
+ * Returns a script-layer value corresponding to the \c mime_matches type.
+ * @param m The MIME match information with which to populate the value.
+ */
+VectorVal* GenMIMEMatchesVal(const RuleMatcher::MIME_Matches& m);
+
 } // namespace file_analysis
 
 extern file_analysis::Manager* file_mgr;