Introduce enum ServiceFlags for service flags

src/main.h

@@ -138,6 +138,8 @@ static const unsigned int MAX_BLOCKS_TO_ANNOUNCE = 8;
 /** Maximum number of unconnecting headers announcements before DoS score */
 static const int MAX_UNCONNECTING_HEADERS = 10;
 
+static const bool DEFAULT_PEERBLOOMFILTERS = true;
+
 struct BlockHasher
 {
     size_t operator()(const uint256& hash) const { return hash.GetCheapHash(); }