Add missing cast

Without the cast we get a spurious UNSAT.

Author: peterschrammel

src/main/java/java/lang/String.java

@@ -4333,7 +4333,7 @@ public static String valueOf(float f) {
      */
     public static String valueOf(double d) {
         // string solver only knows how to convert floats to string
-        return CProverString.toString(d);
+        return CProverString.toString((float)d);
         // return Double.toString(d);
     }