CbmDefs.h: Use fwd declaration of std::ostream.

Replace the relatively heavy iostream with the lightweight alternative iosfwd that provides a forward declaration for std::ostream in CbmDefs.h.

Edit: Also see here, why it's useful to avoid including iostream when it's not needed.

algo/ca/core/tracking/CaFramework.h

@@ -220,6 +220,9 @@ namespace cbm::algo::ca
     Parameters<fvec> fParameters;  ///< Object of Framework parameters class
     InputData fInputData;          ///< Tracking input data
 
+    Vector<unsigned char> fvHitKeyFlags{
+      "Framework::fvHitKeyFlags"};  ///< List of key flags: has been this hit or cluster already used
+
     TrackingMonitorData fMonitorData{};  ///< Tracking monitor data (statistics per call)
 
     int fNofThreads = 1;  ///< Number of threads to execute the track-finder