adding rtx modifications

- get volume curves
- get relative error / n iterations from last solution
- get more tank characteristics
- modify sim duration during active simulation

src/vars.h

@@ -158,6 +158,7 @@ EXTERN Svalve   *Valve;                /* Valve data                   */
 EXTERN Scontrol *Control;              /* Control data                 */
 EXTERN HTtable  *Nht, *Lht;            /* Hash tables for ID labels    */
 EXTERN Padjlist *Adjlist;              /* Node adjacency lists         */
+EXTERN int _relativeError, _iterations; /* Info about hydraulic solution */
 
 /*
 ** NOTE: Hydraulic analysis of the pipe network at a given point in time