Add enforcenodebloom option.

Previously peers which implement a protocol version less than NO_BLOOM_VERSION
would not be disconnected for sending a filter command, regardless of the
peerbloomfilter option.

Many node operators do not wish to provide expensive bloom filtering for SPV
clients, previously they had to cherry pick the commit which enabled the
disconnect logic.

The default should remain false until a sufficient percent of SPV clients
have updated.

src/main.cpp

@@ -3997,12 +3997,10 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         if (pfrom->nVersion >= NO_BLOOM_VERSION) {
             Misbehaving(pfrom->GetId(), 100);
             return false;
+        } else if (GetBoolArg("-enforcenodebloom", false)) {
+            pfrom->fDisconnect = true;
+            return false;
         }
-        //TODO: Enable this after reasonable network upgrade
-        //else {
-        //    pfrom->fDisconnect = true;
-        //    return false;
-        //}
     }