add -timeout default as constant and use them

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

src/netbase.h

@@ -19,6 +19,9 @@
 extern int nConnectTimeout;
 extern bool fNameLookup;
 
+/** -timeout default */
+static const int DEFAULT_CONNECT_TIMEOUT = 5000;
+
 #ifdef WIN32
 // In MSVC, this is defined as a macro, undefine it to prevent a compile and link error
 #undef SetPort