Added plain ncurses backend, for testing
Test code for comparing tim screen output
Multi-line rendering
nc_set_yx() handles long lines
BROKEN FOR SCROLLING: Cursor positioning - skip wrapped lines
buffer_toscreen() handles all buffer -> screen coord'ing
Pull out buffer linewrap calculation
Cursor limits/scrolling take wrapped lines into account
Check begin != NULL before entering linewrap
Clear the line after wrap - prevent scrolls leaving artefacts
Handle cursor movement down after a wrapped line

If this happens we need to count the wrapped line's line-increment, and
use it to apply the limit correctly in ui_cur_changed()
Prevent buffer drawing encroaching into the command line
Motions L and M handle screen lines, not virtual
TEMP: wrap tests
TODO: wrap / visual mode