Alignment should be taken care by the surface pitch and
GL_UNPACK_ROW_LENGTH alone just fine, as long as the pitch is a
multiple of the pixel size. Client APIs respect that,
internally we need to do the same and the changes to
surface_load_texture and wined3d_volume_upload_data are there
for this reason (e.g. WINED3DFMT_R16G16_SNORM is emulated with
GL_RGB16 when NV_texture_shader isn't supported).