[DrJava] Line enumeration is back.

[Jim V. F. <big...@ow...>]

And better than ever.

We've added some caching information (position, line number, previous
newline, and next newline) to DefinitionsDocument, and we're guaranteed
never to do more work than we have to.  If it's cheaper to calculate the
documents position from "scratch" i.e. the top of the document, then it
does that.  Otherwise, it calculates how much earlier or later in the
document the current location is than the cached location, and merges it
with the cached line number.  It's pretty slick;  I've never written
anything quite like it.

There's still an outstanding issue concerning switching documents, you can
read the feature request if you're interested.  But check out the code,
laddies, you can see the line numbers!  (I even threw in some spacing in
the status bar display, so the Mac OS X users can see it.  ;-)

Jim