top: modest efficiency change to message line handling

top: modest efficiency change to message line handling

When the final solution for cursor positioning for all
^Z or ^C cases was introduced the revised placement of
message line management introduced with the window mgr
'screen' refactor was retained. Those two commits mean
that a former tgoto was no longer needed when clearing
that msg line or displaying the scroll coordinate msg.

This patch eliminates the tgoto employed by frame_make
while assimilating a now defunct show_scroll function.

Reference(s):
. final cursor positioning for ^Z or ^C
commit 46a1356219cfab67240704af9cd73b58a20d4232
. 'screen' window manager refactor
commit 0fe393ff270922cd4f6edbcaabba006314e73a37

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