Fix one definition rule violation in ncurses_ui.hh
Fix one definition rule violation in ncurses_ui.hh

The memory domain of Vector<DisplayBuffer> was different depending
on if display_buffer.hh has been included or not.

casimir/kakoune,casimir/kakoune,flavius/kakoune,alexherbo2/kakoune,flavius/kakoune,occivink/kakoune,jkonecny12/kakoune,jjthrash/kakoune,jkonecny12/kakoune,Somasis/kakoune,danr/kakoune,jkonecny12/kakoune,lenormf/kakoune,ekie/kakoune,ekie/kakoune,casimir/kakoune,occivink/kakoune,lenormf/kakoune,mawww/kakoune,jjthrash/kakoune,ekie/kakoune,lenormf/kakoune,occivink/kakoune,casimir/kakoune,ekie/kakoune,flavius/kakoune,mawww/kakoune,Somasis/kakoune,Somasis/kakoune,danr/kakoune,alexherbo2/kakoune,alexherbo2/kakoune,danr/kakoune,jjthrash/kakoune,mawww/kakoune,flavius/kakoune,alexherbo2/kakoune,lenormf/kakoune,mawww/kakoune,occivink/kakoune,jkonecny12/kakoune,danr/kakoune,Somasis/kakoune,jjthrash/kakoune