Revert "Relay double-spends, subject to anti-DOS"

This reverts commit d640a3ceab.

src/main.h

@@ -112,9 +112,6 @@ struct CNodeStateStats;
 
 struct CBlockTemplate;
 
-/** Set up internal signal handlers **/
-void RegisterInternalSignals();
-
 /** Register a wallet to receive updates from core */
 void RegisterWallet(CWalletInterface* pwalletIn);
 /** Unregister a wallet from core */