These sequences have been used "informally" forever, and until recently
mode 1004 was included in Xterm's XM (enable mouse reporting) sequence.
But as of ncurses 6.4 patch 20231028, focus reporting mode is removed
from XM and added to new fe and fd capabilities. Xterm also includes
definitions for the actual focus events ("kxIN" and "kxOUT"), so include
those too.