MFC vt(4) mouse cursor improvements from dumbbell:

MFC vt(4) mouse cursor improvements from dumbbell:

r270269:

  vt(4): Handle global and per-window mouse cursor toggle in one place

  Before the global flag was set/unset using the CONS_MOUSECTL ioctl,
  and the per-window flag through the MOUSE_SETLEVEL or MOUSE_SETMODE
  ioctls.

  Also, if the cursor is already enabled/disabled, return immediatly.
  This avoids to reset the cursor's position to the center of the
  screen.

  This matches syscons' behavior.

  While here, remove a trailing space and a redundant variable
  declaration.

r270271:

  vt(4): Mark cursor old position as dirty before reading the dirty area

  Otherwise, the redraw is done during the next vt_flush run.

r270272:

  vt(4): If the cursor is globally disabled, don't mark its position as dirty

  This avoids unnecessary redraw. In particular, during boot, where the
  cursor is disabled and its fake position is [0;0], this triggered a
  refresh of the whole screen each time vt_flush() is called.

r270273:

  vt(4): If the cursor didn't move, don't mark its position as dirty

  Currently, this has no effect, because the cursor is always redrawn
  anyway. But this will be useful after improvements to the
  vd_bitbltchr_t callback API.

  The vt_device structure members used to store the position of the
  cursor as of the last redraw are renamed from vd_mdirty{x,y} to
  vd_mold{x,y}.  The associated comment is fixed too. Also, their value
  is now expressed in pixels, not in character columns/row.

r270275:

  vt(4): Mark the current cursor position as dirty

  Like r270273, this has no effect for now, because the cursor is always
  drawn. This is in preparation of future changes to vd_bitbltchr_t API.

r270278:

  vt(4): Mark cursor position as dirty when we enable/disable it

Sponsored by:	The FreeBSD Foundation

git-svn-id: svn://svn.freebsd.org/base/stable/10@271022 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f