bug#19342: auto-fill scan-error in sh-mode

[Stefan Monnier]

> Any comments?

Looks OK to me.  Tho maybe in the interest of minimizing the indentation
depth (and the amount of text changes in the patch), maybe we could
just use something like:

    (let ((newcol (condition-case nil
                      (smie-indent-calculate)
                    (scan-error (point-max))))
      [...]

where `point-max` is just a large enough value that the subsequent
computation of `newgain` leads to skipping this choice.


        Stefan