Added libigl library files (header-only library)

xs/src/igl/dot.cpp

@@ -0,0 +1,16 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2013 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 "dot.h"
+
+// http://www.antisphere.com/Wiki/tools:anttweakbar
+IGL_INLINE double igl::dot(
+  const double *a, 
+  const double *b)
+{
+  return a[0]*b[0] + a[1]*b[1] + a[2]*b[2];
+}