kernal routine does not work, when the cursor is not at the same position
where it was switched on, because when switching it on, the kernal remembers
the character attribute and restores this when switching it off. So characters
may get the wrong attribute. The solution is to always switch the cursor on,
before switching it off.
git-svn-id: svn://svn.cc65.org/cc65/trunk@4592 b7a2c559-68d2-44c3-8de9-860c34a00d81