Litecoin: Reduce high priority tx size limit to 5KB

This is the first step in making the high priority transaction area
available to more people.  Future versions of Litecoin will eventually
reduce this to 1KB per tx to match Bitcoin 0.8.6+.

src/main.cpp

@@ -908,7 +908,7 @@ CAmount GetMinRelayFee(const CTransaction& tx, unsigned int nBytes, bool fAllowF
         // * If we are relaying we allow transactions up to DEFAULT_BLOCK_PRIORITY_SIZE - 1000
         //   to be considered to fall into this category. We don't want to encourage sending
         //   multiple transactions instead of one big transaction to avoid fees.
-        if (nBytes < (DEFAULT_BLOCK_PRIORITY_SIZE - 1000))
+        if (nBytes < (DEFAULT_BLOCK_PRIORITY_SIZE - 5000))
             nMinFee = 0;
     }