Block display elements that can take the position attribute, and thus may be floating as opposed to fixed in narrative position in an article [or book]. Created for use as the content of <floats-group>.
<!ENTITY % floats-display.class "alternatives | boxed-text | chem-struct-wrap | code | fig | fig-group | graphic | media | preformat | supplementary-material | table-wrap | table-wrap-group" >