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/solid_angle.h

@@ -0,0 +1,29 @@
+#ifndef IGL_SOLID_ANGLE_H
+#define IGL_SOLID_ANGLE_H
+#include "igl_inline.h"
+#include <Eigen/Dense>
+namespace igl
+{
+  // Compute the signed solid angle subtended by the oriented 3d triangle (A,B,C) at some point P
+  // 
+  // Inputs:
+  //   A  3D position of corner 
+  //   B  3D position of corner 
+  //   C  3D position of corner 
+  //   P  3D position of query point
+  // Returns signed solid angle
+  template <
+    typename DerivedA,
+    typename DerivedB,
+    typename DerivedC,
+    typename DerivedP>
+  IGL_INLINE typename DerivedA::Scalar solid_angle(
+    const Eigen::MatrixBase<DerivedA> & A,
+    const Eigen::MatrixBase<DerivedB> & B,
+    const Eigen::MatrixBase<DerivedC> & C,
+    const Eigen::MatrixBase<DerivedP> & P);
+}
+#ifndef IGL_STATIC_LIBRARY
+#  include "solid_angle.cpp"
+#endif
+#endif