add -timeout default as constant and use them

- update help message text
- simplify code in init to check for -timeout

src/netbase.cpp

@@ -40,7 +40,7 @@ using namespace std;
 static proxyType proxyInfo[NET_MAX];
 static CService nameProxy;
 static CCriticalSection cs_proxyInfos;
-int nConnectTimeout = 5000;
+int nConnectTimeout = DEFAULT_CONNECT_TIMEOUT;
 bool fNameLookup = false;
 
 static const unsigned char pchIPv4[12] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff };