rename fNoListen to fListen and move to net

- better code readability and it belongs to net
- this is a prerequisite for a pull to add -listen to the GUI

src/net.h

@@ -105,6 +105,7 @@ CAddress GetLocalAddress(const CNetAddr *paddrPeer = NULL);
 
 
 extern bool fDiscover;
+extern bool fListen;
 extern uint64_t nLocalServices;
 extern uint64_t nLocalHostNonce;
 extern CAddrMan addrman;