Reconcile with changes in line movement behavior for long text lines

Reconcile with changes in line movement behavior for long text lines
that cross more than a single physical window line, ie when truncate-lines
is nil.

(allout-next-visible-heading): Provide for change in line-move behavior on
long lines when truncate-lines is nil.  In that case, line-move can wind up
on the same textual line when it moves to the next window line, and moving
to the bullet position after the move yields zero advancement.  Add logic
to detect and compensate for the lack of progress.

(allout-current-topic-collapsed-p): move-end-of-line respect for field
boundaries is different when operating with body lines shorter than window
width versus ones greater than window width, which can yield false
negatives in this function.  Avoid difference by applying move-end-of-line
while field-text-motion is inhibited.