Refactor folder (#10475)

Move many third-party components' source codes from the src folder to a new folder called deps_src. The goal is to make the code structure clearer and easier to navigate.

deps_src/libigl/igl/is_planar.cpp

@@ -0,0 +1,18 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2014 Alec Jacobson <alecjacobson@gmail.com>
+// 
+// This Source Code Form is subject to the terms of the Mozilla Public License 
+// v. 2.0. If a copy of the MPL was not distributed with this file, You can 
+// obtain one at http://mozilla.org/MPL/2.0/.
+#include "is_planar.h"
+IGL_INLINE bool igl::is_planar(const Eigen::MatrixXd & V)
+{
+  if(V.size() == 0) return false;
+  if(V.cols() == 2) return true;
+  for(int i = 0;i<V.rows();i++)
+  {
+    if(V(i,2) != 0) return false;
+  }
+  return true;
+}