Send --help message to stdout i.s.o stderr

This allows fun stuff such as `bitcoin --help | less`, and more
easy piping to files.

Looking at other tools such as bash, gcc, they all send their help
text to stdout.

src/init.cpp

@@ -144,7 +144,7 @@ bool AppInit(int argc, char* argv[])
 
             strUsage += "\n" + HelpMessage();
 
-            fprintf(stderr, "%s", strUsage.c_str());
+            fprintf(stdout, "%s", strUsage.c_str());
             return false;
         }
 

src/qt/guiutil.cpp

@@ -439,7 +439,7 @@ void HelpMessageBox::printToConsole()
 {
     // On other operating systems, the expected action is to print the message to the console.
     QString strUsage = header + "\n" + coreOptions + "\n" + uiOptions;
-    fprintf(stderr, "%s", strUsage.toStdString().c_str());
+    fprintf(stdout, "%s", strUsage.toStdString().c_str());
 }
 
 void HelpMessageBox::showOrPrint()