Document -debugnet option in command line help.

Fixes #1507

src/init.cpp

@@ -256,7 +256,8 @@ std::string HelpMessage()
         "  -daemon                " + _("Run in the background as a daemon and accept commands") + "\n" +
 #endif
         "  -testnet               " + _("Use the test network") + "\n" +
-        "  -debug                 " + _("Output extra debugging information") + "\n" +
+        "  -debug                 " + _("Output extra debugging information. Implies all other -debug* options") + "\n" +
+        "  -debugnet              " + _("Output extra network debugging information") + "\n" +
         "  -logtimestamps         " + _("Prepend debug output with timestamp") + "\n" +
         "  -printtoconsole        " + _("Send trace/debug info to console instead of debug.log file") + "\n" +
 #ifdef WIN32