bug #256: enable vectorization with unaligned loads/stores.

This concerns all architectures and all sizes.
This new behavior can be disabled by defining EIGEN_UNALIGNED_VECTORIZE=0

Eigen/src/Core/util/Macros.h

@@ -756,6 +756,11 @@ namespace Eigen {
 #define EIGEN_DEFAULT_ALIGN_BYTES EIGEN_MAX_ALIGN_BYTES
 #endif
 
+
+#ifndef EIGEN_UNALIGNED_VECTORIZE
+#define EIGEN_UNALIGNED_VECTORIZE 1
+#endif
+
 //----------------------------------------------------------------------