Patch from Paul Fox to fix the reported vi status line problems.

Patch from Paul Fox to fix the reported vi status line problems.

Paul writes:

the bugs were being caused because when edit_status() and/or
show_status_line() were being called, the current status wasn't
always yet up to date.  i've changed things so that the
formatting/checking/displaying of the status line occurs more
rigorously as the last thing before the user is asked for input.
i did some minor optimization so we don't have to count the
file's lines every time, but this could be improved.  (yes, i
know that turning file_modified into a counter will cause it to
be wrong once in blue moon.  i'm willing to risk that.  ymmv.
this could be fixed with the addition of one more boolean.)