Keep first three original testnet fr addresses so existing coinbase

transactions on testnet remain valid during upgrade.  New addresses
will be used starting from block 53127.

src/chainparams.cpp

@@ -267,7 +267,7 @@ public:
 
         // Founders reward script expects a vector of 2-of-3 multisig addresses
         vFoundersRewardAddress = {
-            "t2Mcc7khmWtviJKZLn9XyqPcs2zfQDn5K4X", "t2M29JPXXM8p97jFHexpVRuKBZxjLcXseey", "t26eA72uzJbHroLGgbWq9ZxCPu4keAFMP54", "t2ENg7hHVqqs9JwU5cgjvSbxnT2a9USNfhy", 
+            "t2UNzUUx8mWBCRYPRezvA363EYXyEpHokyi", "t2N9PH9Wk9xjqYg9iin1Ua3aekJqfAtE543", "t2NGQjYMQhFndDHguvUw4wZdNdsssA6K7x2", "t2ENg7hHVqqs9JwU5cgjvSbxnT2a9USNfhy",
             "t2BkYdVCHzvTJJUTx4yZB8qeegD8QsPx8bo", "t2J8q1xH1EuigJ52MfExyyjYtN3VgvshKDf", "t2Crq9mydTm37kZokC68HzT6yez3t2FBnFj", "t2EaMPUiQ1kthqcP5UEkF42CAFKJqXCkXC9", 
             "t2F9dtQc63JDDyrhnfpzvVYTJcr57MkqA12", "t2LPirmnfYSZc481GgZBa6xUGcoovfytBnC", "t26xfxoSw2UV9Pe5o3C8V4YybQD4SESfxtp", "t2D3k4fNdErd66YxtvXEdft9xuLoKD7CcVo", 
             "t2DWYBkxKNivdmsMiivNJzutaQGqmoRjRnL", "t2C3kFF9iQRxfc4B9zgbWo4dQLLqzqjpuGQ", "t2MnT5tzu9HSKcppRyUNwoTp8MUueuSGNaB", "t2AREsWdoW1F8EQYsScsjkgqobmgrkKeUkK", 

src/gtest/test_foundersreward.cpp

@@ -100,12 +100,16 @@ TEST(founders_reward_test, general) {
 
     CChainParams params = Params();
     
-    // First testnet reward:
-    // address = t2Mcc7khmWtviJKZLn9XyqPcs2zfQDn5K4X
-    // script.ToString() = OP_HASH160 a541a6cbddeb5ff69c10d91008ac56247906f08d OP_EQUAL
-    // HexStr(script) = a914a541a6cbddeb5ff69c10d91008ac56247906f08d87
-    EXPECT_EQ(params.GetFoundersRewardScriptAtHeight(1), ParseHex("a914a541a6cbddeb5ff69c10d91008ac56247906f08d87"));
-    EXPECT_EQ(params.GetFoundersRewardAddressAtHeight(1), "t2Mcc7khmWtviJKZLn9XyqPcs2zfQDn5K4X");
+    // Fourth testnet reward:
+    // address = t2ENg7hHVqqs9JwU5cgjvSbxnT2a9USNfhy
+    // script.ToString() = OP_HASH160 55d64928e69829d9376c776550b6cc710d427153 OP_EQUAL
+    // HexStr(script) = a91455d64928e69829d9376c776550b6cc710d42715387
+    EXPECT_EQ(params.GetFoundersRewardScriptAtHeight(1), ParseHex("a914ef775f1f997f122a062fff1a2d7443abd1f9c64287"));
+    EXPECT_EQ(params.GetFoundersRewardAddressAtHeight(1), "t2UNzUUx8mWBCRYPRezvA363EYXyEpHokyi");
+    EXPECT_EQ(params.GetFoundersRewardScriptAtHeight(53126), ParseHex("a914ac67f4c072668138d88a86ff21b27207b283212f87"));
+    EXPECT_EQ(params.GetFoundersRewardAddressAtHeight(53126), "t2NGQjYMQhFndDHguvUw4wZdNdsssA6K7x2");
+    EXPECT_EQ(params.GetFoundersRewardScriptAtHeight(53127), ParseHex("a91455d64928e69829d9376c776550b6cc710d42715387"));
+    EXPECT_EQ(params.GetFoundersRewardAddressAtHeight(53127), "t2ENg7hHVqqs9JwU5cgjvSbxnT2a9USNfhy");
 
     int maxHeight = params.GetConsensus().GetLastFoundersRewardBlockHeight();