fixes for header

optimise.h

@@ -14,6 +14,7 @@
 
 #include <cmath>
 #include "newmatap.h"
+#include "string"
 
 using namespace NEWMAT;
 
@@ -28,7 +29,7 @@ float optimise1d(ColumnVector &pt, const ColumnVector dir,
  float optimise(ColumnVector &pt, int numopt, const ColumnVector &tol, 
 		float (*func)(const ColumnVector &), int &iterations_done, 
 		int max_iter, const ColumnVector& boundguess, 
-		const string type="brent");
+		const std::string type="brent");
 
 }