fill out the CarSales functions

benchmark/src/main/java/org/capnproto/benchmark/Common.java

@@ -10,10 +10,20 @@ public class Common {
             this.state = 1013904223;
         }
 
-        public int next_int() {
+        public int nextInt() {
             this.state = this.a * this.state + c;
             return this.state;
         }
+
+        public int nextLessThan(int range) {
+            // sign?
+            return this.nextInt() % range;
+        }
+
+        public double nextDouble(double range) {
+            // XXX sign?
+            return (double) this.nextInt() * range / (double)(0xffffffffL);
+        }
     }
 
 }

runtime/src/main/java/org/capnproto/StructList.java

@@ -34,6 +34,10 @@ public final class StructList {
             this.factory = factory;
         }
 
+        public int size() {
+            return this.builder.size();
+        }
+
         public final T get(int index) {
             return this.factory.fromStructBuilder(this.builder.getStructElement(index));
         }