function: push_val_val2 -- shift val down stack
keyboard equivalent: [none]

Copy current data at each vertex, vertex[i].val,
to vertex[i].val2 (push down stack).  Do this to
read in second val to top of stack.  For example,
to read, smooth, and display complex data:

  READ imaginary valfile
  PUSH
  READ real valfile
  SMOOTH val

Here are tcl script commands to read, smooth, and
display complex data (used in polar/eccen/twocond
scripts):

  setfile val */scan1/imaginary-valfile.w
  [or: set val /some/imaginary-valfile.w
  read_binary_values
  smooth_val 10
  push_val_val2
  setfile val */scan1/real-valfile.w
  [or: set val /some/real-valfile.w
  read_binary_values
  smooth_val 10
  redraw

See also:

  swap_val_val2               swap real and imag.
  swap_valval2_valbakval2bak  swap 2 complex nums
  swap_stat_val               swap stat and val
