* add Gael copyright lines on 2 more files

* macro renaming: EIGEN_NDEBUG becomes EIGEN_NO_DEBUG
  as this is much better (and similar to Qt) and
  EIGEN_CUSTOM_ASSERT becomes EIGEN_USE_CUSTOM_ASSERT
* protect Core header by a EIGEN_CORE_H

Eigen/Core

@@ -1,7 +1,10 @@
+#ifndef EIGEN_CORE_H
+#define EIGEN_CORE_H
+
 #include <cstdlib>
 #include <cmath>
 #include <complex>
-#ifndef EIGEN_CUSTOM_ASSERT
+#ifndef EIGEN_USE_CUSTOM_ASSERT
 #include <cassert>
 #endif
 #include <iostream>
@@ -43,3 +46,4 @@ namespace Eigen {
 
 } // namespace Eigen
 
+#endif // EIGEN_CORE_H