Fix off-by-one in extend_line_above (#3689)

`extend_line_above` (and `extend_line` when facing backwards) skip
a line when the current range does not fully cover a line.

Before this change:

    foo
    b#[|a]#r
    baz

With `extend_line_above` or `extend_line` selected the line above.

    #[|foo
    bar]#
    baz

Which is inconsistent with `extend_line_below`. This commit changes
the behavior to select the current line when it is not already
selected.

    foo
    #[|bar]#
    baz

Then further calls of `extend_line_above` extend the selection up
line-wise.

0 files changed, 0 insertions, 0 deletions