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function: clear_ripflags -- undo all cuts
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keyboard equivalent: none

The "ALL" button (lower right) first clears all
cuts (ripflags) including those that might have
been read in at tksurfer startup.

It also clears any patch (surface subset) that
was read in ($flag2d is set to 0).

Finally, it re-reads the surface and curvature,
and restores lateral pose.

"ALL" leaves current vertex data (if any) intact.

Command to do this in tcl script:

  clear_ripflags
  read_binary_surface
  read_binary_curv
  set flag2d 0
  restore
  redrawbutton
