Add json_compact log type for compact/minified JSON.

The "json_compact" log type logs one event per line in compact/minified
JSON format.  GitHub issue #357.

plugins/sudoers/def_data.h

@@ -338,6 +338,7 @@ enum def_tuple {
     kernel,
     sudo,
     json,
+    json_compact,
     dso,
     trace
 };