Added optional support for Sparkfun SiGe GN3S USB GPS RF sampler:

- Added a pre-compiled custom GN3S firmware.
- Added a fully-compliant GNU Radio source block for GN3S USB dongle. It can be used also from GNU Radio companion and from Python applications.
- Added a new GN3S_Signal_Source block. It is possible to disable the GN3S signal source compilation. See README.

git-svn-id: https://svn.code.sf.net/p/gnss-sdr/code/trunk@217 64b25241-fba3-4117-9849-534c7e92360d

drivers/gr-gn3s/include/gn3s_api.h

@@ -0,0 +1,42 @@
+/*!
+ * \file gn3s_api.h
+ * \brief GNU Radio source block to acces to SiGe GN3S USB sampler.
+ * \author Javier Arribas, 2012. jarribas(at)cttc.es
+ *
+ * -------------------------------------------------------------------------
+ *
+ * Copyright (C) 2010-2012  (see AUTHORS file for a list of contributors)
+ *
+ * GNSS-SDR is a software defined Global Navigation
+ *          Satellite Systems receiver
+ *
+ * This file is part of GNSS-SDR.
+ *
+ * GNSS-SDR is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * at your option) any later version.
+ *
+ * GNSS-SDR is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * -------------------------------------------------------------------------
+ */
+
+#ifndef INCLUDED_GN3S_API_H
+#define INCLUDED_GN3S_API_H
+
+#include <gruel/attributes.h>
+
+#ifdef gr_gn3s_EXPORTS
+#  define GN3S_API __GR_ATTR_EXPORT
+#else
+#  define GN3S_API __GR_ATTR_IMPORT
+#endif
+
+#endif /* INCLUDED_GN3S_API_H */