Moved standalone from src to samples

samples/standalone/model/model_rk3.h

@@ -0,0 +1,33 @@
+/*
+    Copyright (C) 2014-2020, Johannes Pekkila, Miikka Vaisala.
+
+    This file is part of Astaroth.
+
+    Astaroth 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.
+
+    Astaroth 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 Astaroth.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/**
+ * @file
+ * \brief Brief info.
+ *
+ * Detailed info.
+ *
+ */
+#pragma once
+#include "astaroth.h"
+#include "modelmesh.h"
+
+void model_rk3(const ModelScalar dt, ModelMesh* mesh);
+
+void model_rk3_step(const int step_number, const ModelScalar dt, ModelMesh* mesh);