Merge #7184: Implement SequenceLocks functions for BIP 68

b043c4b fix sdaftuar's nits again (Alex Morcos)
a51c79b Bug fix to RPC test (Alex Morcos)
da6ad5f Add RPC test exercising BIP68 (mempool only) (Suhas Daftuar)
c6c2f0f Implement SequenceLocks functions (Alex Morcos)

src/consensus/consensus.h

@@ -13,8 +13,11 @@ static const unsigned int MAX_BLOCK_SIGOPS = MAX_BLOCK_SIZE/50;
 /** Coinbase transaction outputs can only be spent after this number of new blocks (network rule) */
 static const int COINBASE_MATURITY = 100;
 
-/** Flags for LockTime() */
+/** Flags for nSequence and nLockTime locks */
 enum {
+    /* Interpret sequence numbers as relative lock-time constraints. */
+    LOCKTIME_VERIFY_SEQUENCE = (1 << 0),
+
     /* Use GetMedianTimePast() instead of nTime for end point timestamp. */
     LOCKTIME_MEDIAN_TIME_PAST = (1 << 1),
 };