discard vectorization in matrix-vector product when data is not even

aligned on the scalar type size (e.g., for double on 32 bits system without -malign-double)

test/testsuite.cmake

@@ -177,7 +177,7 @@ if(WIN32 AND NOT UNIX)
     SET (CTEST_INITIAL_CACHE "
       MAKECOMMAND:STRING=nmake -i
       CMAKE_MAKE_PROGRAM:FILEPATH=nmake
-      CMAKE_GENERATOR:INTERNAL=NMake Makefiles  
+      CMAKE_GENERATOR:INTERNAL=NMake Makefiles
       CMAKE_BUILD_TYPE:STRING=Release
       BUILDNAME:STRING=${EIGEN_BUILD_STRING}
       SITE:STRING=${EIGEN_SITE}