Made autologin optional at compile time

Autologin is disabled by default at compile time, and a warning to
discourage it's usage is printed if it is enabled.
This will make default RetroShare build safer and reduce dependencies as
example we don't depends anymore on gnome keyring is not needed in default
build for linux anymore.

retroshare-gui/src/gui/StartDialog.h

@@ -40,10 +40,12 @@ protected:
 private slots:
 	void loadPerson();
 
+#ifdef RS_AUTOLOGIN
 	/**
 	 * Warns the user that autologin is not secure
 	 */
 	void notSecureWarning();
+#endif // RS_AUTOLOGIN
 
 	void on_labelProfile_linkActivated(QString link);