Matrix: adjust buffer size calculation to account for additional characters

Note: If the buffer is too small there's no memory corruption because of the snprintf limit but part of the output gets missing.

matrix/Matrix.hpp

@@ -286,7 +286,7 @@ public:
 
     void print() const
     {
-        static const size_t n = 10*N*M;
+        static const size_t n = 11*N*M + M; // for every entry a tab and 10 digits, for every row a newline
         char * buf = new char[n];
         write_string(buf, n);
         printf("%s\n", buf);