Previously, the "precedes" character would be rendered on every row
when w_skipcol > 0 (i.e., when viewing a single line longer than the
entire screen), instead of just on the first row. Make sure to only
render it on the first row in this case.
Add a test for this behavior.
Fix documentation for the "precedes" character, which erroneously
stated that it was only active when wrap mode was off.
dd7206af37
