terminal_image <-
isearch_other_style: style*style applied to the matches on the screen other than the
one the user is on, or @nil
to leave them alone. It serves an incremental search and a selection
alike: what a search is looking for while one runs, and otherwise the
selected text (see terminal_image<-selection_string).
Only the visible ones: they are worked out afresh every time the window
is painted, so scrolling brings the ones it reaches into view without
the search or the selection doing anything about it.
