MFC r226099:

MFC r226099:

  Tab should not blank cells.

  It seems I was under the impression that a tab differs from a single
  forward tabulation, namely that it blanks the underlying cells. This
  seems not to be the case. They are identical.

  This should fix applications like jove(1) that use tabs instead of
  explicit cursor position setting.

  Reported by:  Brett Glass <brett lariat net>

MFC r226183:

  Properly use the cursor to bound the position for CUP.

  We must take the origin region into account when clamping the cursor
  position.

Approved by:	re@ (kib)

git-svn-id: svn://svn.freebsd.org/base/stable/9@226295 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f