Auto merge of #2342 - bitcartel:1081__mempoolpatch, r=str4d

Add ability for node to reject tx from mempool by number of tx inputs

Implement short-term solution described in #2343 so that users can respond promptly to critical short-term problems caused by quadratic validation scaling, such as the getblocktemplate latency, block propagation latency, and mempool size inflation issues described in #2333.

qa/pull-tester/rpc-tests.sh

@@ -26,6 +26,7 @@ testScripts=(
     'rest.py'
     'mempool_spendcoinbase.py'
     'mempool_coinbase_spends.py'
+    'mempool_tx_input_limit.py'
     'httpbasics.py'
     'zapwallettxes.py'
     'proxy_test.py'