Building igl statically and moving to the dep scripts

Fixing dep build script on Windows and removing some warnings.

Use bundled igl by default.

Not building with the dependency scripts if not explicitly stated. This way, it will stay in
Fix the libigl patch to include C source files in header only mode.

src/libigl/igl/eigs.h

@@ -0,0 +1,61 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2016 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/.
+#ifndef IGL_EIGS_H
+#define IGL_EIGS_H
+#include "igl_inline.h"
+#include <Eigen/Core>
+#include <Eigen/Sparse>
+
+namespace igl
+{
+  // Act like MATLAB's eigs function. Compute the first/last k eigen pairs of
+  // the generalized eigen value problem:
+  //
+  //     A u = s B u
+  //
+  // Solutions are approximate and sorted. 
+  //
+  // Ideally one should use ARPACK and the Eigen unsupported ARPACK module.
+  // This implementation does simple, naive power iterations.
+  //
+  // Inputs:
+  //   A  #A by #A symmetric matrix
+  //   B  #A by #A symmetric positive-definite matrix
+  //   k  number of eigen pairs to compute
+  //   type  whether to extract from the high or low end
+  // Outputs:
+  //   sU  #A by k list of sorted eigen vectors (descending)
+  //   sS  k list of sorted eigen values (descending)
+  //
+  // Known issues:
+  //   - only the 'sm' small magnitude eigen values are well supported
+  //   
+  enum EigsType
+  {
+    EIGS_TYPE_SM = 0,
+    EIGS_TYPE_LM = 1,
+    NUM_EIGS_TYPES = 2
+  };
+  template <
+    typename Atype,
+    typename Btype,
+    typename DerivedU,
+    typename DerivedS>
+  IGL_INLINE bool eigs(
+    const Eigen::SparseMatrix<Atype> & A,
+    const Eigen::SparseMatrix<Btype> & B,
+    const size_t k,
+    const EigsType type,
+    Eigen::PlainObjectBase<DerivedU> & sU,
+    Eigen::PlainObjectBase<DerivedS> & sS);
+}
+
+#ifndef IGL_STATIC_LIBRARY
+#include "eigs.cpp"
+#endif
+#endif