Add SB Curated (copied from the smartbugs repository).

dataset/arithmetic/integer_overflow_1.sol

@@ -0,0 +1,24 @@
+/*
+ * @source: https://github.com/trailofbits/not-so-smart-contracts/blob/master/integer_overflow/integer_overflow_1.sol
+ * @author: -
+ * @vulnerable_at_lines: 14
+ */
+
+ pragma solidity ^0.4.15;
+
+ contract Overflow {
+     uint private sellerBalance=0;
+
+     function add(uint value) returns (bool){
+         // <yes> <report> ARITHMETIC
+         sellerBalance += value; // possible overflow
+
+         // possible auditor assert
+         // assert(sellerBalance >= value);
+     }
+
+  // function safe_add(uint value) returns (bool){
+  //   require(value + sellerBalance >= sellerBalance);
+  // sellerBalance += value;
+  // } 
+ }