Added additional upgrade mechanisms for deployment

contracts/Synth.sol

@@ -289,6 +289,14 @@ contract Synth is ExternStateToken {
         emitBurned(account, amount);
     }
 
+    // Allow owner to set the total supply on import.
+    function setTotalSupply(uint amount)
+        external
+        optionalProxy_onlyOwner
+    {
+        totalSupply = amount;
+    }
+
     // Allow synthetix to trigger a token fallback call from our synths so users get notified on
     // exchange as well as transfer
     function triggerTokenFallbackIfNeeded(address sender, address recipient, uint amount)

contracts/SynthetixState.sol

@@ -71,6 +71,9 @@ contract SynthetixState is State, LimitedSetup {
     // Global debt pool tracking
     uint[] public debtLedger;
 
+    // Import state
+    uint public importedXDRAmount;
+
     // A quantity of synths greater than this ratio
     // may not be issued against a given value of SNX.
     uint public issuanceRatio = SafeDecimalMath.unit() / 5;
@@ -210,12 +213,15 @@ contract SynthetixState is State, LimitedSetup {
         // What is the value of the requested debt in XDRs?
         uint xdrValue = synthetix.effectiveValue("sUSD", amount, "XDR");
 
-        // What is the value of all issued synths of the system (priced in XDRs)?
-        uint totalDebtIssued = synthetix.totalIssuedSynths("XDR");
+        // What is the value that we've previously imported?
+        uint totalDebtIssued = importedXDRAmount;
 
         // What will the new total be including the new value?
         uint newTotalDebtIssued = xdrValue.add(totalDebtIssued);
 
+        // Save that for the next import.
+        importedXDRAmount = newTotalDebtIssued;
+
         // What is their percentage (as a high precision int) of the total debt?
         uint debtPercentage = xdrValue.divideDecimalRoundPrecise(newTotalDebtIssued);