Fixed missing include for gcc

Former-commit-id: 3cf040d87c

src/solver/AbstractEquationSolver.h

@@ -2,6 +2,7 @@
 #define STORM_SOLVER_ABSTRACTEQUATIONSOLVER_H_
 
 #include "src/solver/TerminationCondition.h"
+#include <memory>
 
 namespace storm {
     namespace solver {
@@ -50,4 +51,4 @@ namespace storm {
     }
 }
 
-#endif /* STORM_SOLVER_ABSTRACTEQUATIONSOLVER_H_ */
+#endif /* STORM_SOLVER_ABSTRACTEQUATIONSOLVER_H_ */