Add IsReachable(net) function

Allows other parts of the program to query for reachable
status of a network. Similar to IsLimited(net).

src/net.cpp

@@ -307,12 +307,18 @@ bool IsLocal(const CService& addr)
     return mapLocalHost.count(addr) > 0;
 }
 
+/** check whether a given network is one we can probably connect to */
+bool IsReachable(enum Network net)
+{
+    LOCK(cs_mapLocalHost);
+    return vfReachable[net] && !vfLimited[net];
+}
+
 /** check whether a given address is in a network we can probably connect to */
 bool IsReachable(const CNetAddr& addr)
 {
-    LOCK(cs_mapLocalHost);
     enum Network net = addr.GetNetwork();
-    return vfReachable[net] && !vfLimited[net];
+    return IsReachable(net);
 }
 
 bool GetMyExternalIP2(const CService& addrConnect, const char* pszGet, const char* pszKeyword, CNetAddr& ipRet)

src/net.h

@@ -106,6 +106,7 @@ bool AddLocal(const CNetAddr& addr, int nScore = LOCAL_NONE);
 bool SeenLocal(const CService& addr);
 bool IsLocal(const CService& addr);
 bool GetLocal(CService &addr, const CNetAddr *paddrPeer = NULL);
+bool IsReachable(enum Network net);
 bool IsReachable(const CNetAddr &addr);
 void SetReachable(enum Network net, bool fFlag = true);
 CAddress GetLocalAddress(const CNetAddr *paddrPeer = NULL);