top: refactor 'mkVIZ' support to avoid future problems

top: refactor 'mkVIZ' support to avoid future problems

In the patch referenced below, 2 potential abends were
fixed both of which involved 'alternate display mode'.

The root cause of those abends was a negative value in
the 'begnext' field for other than the current window.

And while that potential is fixed for now the existing
code almost invites such problems again in the future.

So, this patch will remove any temptation to name some
other window in the 'mkVIZrow1' macro. And, since that
macro is not the only source of 'begnext' changes, the
'mkVizrowX' is being added to identify such occasions.

[ and for symmetry i've added a 'mkVIZyes' macro and ]
[ ameliorated an otherwise surreptitious assignment! ]

Reference(s):
commit 84e85611c36d31a478e1b62e5668671d9389265d

Signed-off-by: Jim Warner <james.warner@comcast.net>