Replace CBlockHeader::GetHash with call to SerializeHash

Removes variability between LE and BE.
As suggested by @sipa.

adapted from bitcoin/bitcoin@a0ae79d

src/primitives/block.cpp

@@ -15,8 +15,8 @@
 
 uint256 CBlockHeader::GetHash() const
 {
-#if defined(WORDS_BIGENDIAN)
     if (nVersion < 4)  {
+#if defined(WORDS_BIGENDIAN)
         uint8_t data[80];
         WriteLE32(&data[0], nVersion);
         memcpy(&data[4], hashPrevBlock.begin(), hashPrevBlock.size());
@@ -25,36 +25,12 @@ uint256 CBlockHeader::GetHash() const
         WriteLE32(&data[72], nBits);
         WriteLE32(&data[76], nNonce);
         return HashQuark(data, data + 80);
-    } else if (nVersion < 7) {
-        uint8_t data[112];
-        WriteLE32(&data[0], nVersion);
-        memcpy(&data[4], hashPrevBlock.begin(), hashPrevBlock.size());
-        memcpy(&data[36], hashMerkleRoot.begin(), hashMerkleRoot.size());
-        WriteLE32(&data[68], nTime);
-        WriteLE32(&data[72], nBits);
-        WriteLE32(&data[76], nNonce);
-        memcpy(&data[80], hashMerkleRoot.begin(), hashMerkleRoot.size());
-        return Hash(data, data + 80);
-    } else {
-        uint8_t data[80];
-        WriteLE32(&data[0], nVersion);
-        memcpy(&data[4], hashPrevBlock.begin(), hashPrevBlock.size());
-        memcpy(&data[36], hashMerkleRoot.begin(), hashMerkleRoot.size());
-        WriteLE32(&data[68], nTime);
-        WriteLE32(&data[72], nBits);
-        WriteLE32(&data[76], nNonce);
-        return Hash(data, data + 80);
-    }
-
 #else // Can take shortcut for little endian
-    if (nVersion < 4)
         return HashQuark(BEGIN(nVersion), END(nNonce));
-
-    if (nVersion < 7)
-        return Hash(BEGIN(nVersion), END(nAccumulatorCheckpoint));
-
-    return Hash(BEGIN(nVersion), END(nNonce));
 #endif
+    }
+    // version >= 4
+    return SerializeHash(*this);
 }
 
 std::string CBlock::ToString() const