top: plug a minor hole in the vertical scrolling logic

In that commit referenced below, a few edge cases were
addressed regarding vertical positioning involving any
'hidden' tasks. But, 2 additional edge cases remained.

In a running top, if the user employed 'other filters'
(o/O) or 'user filters' (u/U) proper vertical position
was not ensured. And, while this could be easily fixed
by striking the home/end or up/down arrow keys, it was
very poor etiquette to shift this burden to the users.

So, this patch plugs that gap, automating the process.

Reference(s):
commit 9d59ddc466

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

top/top.h

@@ -390,7 +390,7 @@ typedef struct WIN_t {
 #endif
 
         // Support for a proper (visible) row #1 whenever Curwin changes
-        // ( or a certain vertical scrolling key has been struck )
+        // ( or a key which might affect vertical scrolling was struck )
 #define mkVIZrow1(q) { q->begtask -= 1; q->begnext = +1; }
 
         /* Special Section: end ------------------------------------------ */