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/is_writable.cpp

@@ -0,0 +1,58 @@
+// 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 "is_writable.h"
+
+#ifdef _WIN32
+#include <sys/stat.h>
+#ifndef S_IWUSR
+#  define S_IWUSR S_IWRITE
+#endif
+IGL_INLINE bool is_writable(const char* filename)
+{
+  // Check if file already exists
+  struct stat status;
+  if(stat(filename,&status)!=0)
+  {
+    return false;
+  }
+
+  return S_IWUSR & status.st_mode;
+}
+#else
+#include <sys/stat.h>
+#include <unistd.h>
+
+IGL_INLINE bool igl::is_writable(const char* filename)
+{
+  // Check if file already exists
+  struct stat status;
+  if(stat(filename,&status)!=0)
+  {
+    return false;
+  }
+
+  // Get current users uid and gid
+  uid_t this_uid = getuid();
+  gid_t this_gid = getgid();
+
+  // Dealing with owner
+  if( this_uid == status.st_uid )
+  {
+    return S_IWUSR & status.st_mode;
+  }
+
+  // Dealing with group member
+  if( this_gid == status.st_gid )
+  {
+    return S_IWGRP & status.st_mode;
+  }
+
+  // Dealing with other
+  return S_IWOTH & status.st_mode;
+}
+#endif