Simplify raw_buffer's destructor just a tad.
Simplify raw_buffer's destructor just a tad.

--HG--
extra : convert_revision : svn%3A83215879-3e5a-4751-8c9d-778f44bb06a5/trunk%40376

jbrownbridge/thrust,jbrownbridge/thrust,jbrownbridge/thrust,jbrownbridge/thrust