[DrJava] Line numbers committed.

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

The mist cleared, the debugger group needed a certain implementation, and
lo, it became.

getCurrentLine() and getCurrentCol() have been added to
DefinitionsDocument, and a PositionField inner class has been created in
MainFrame to store the results of calls to those methods.

Right now, the results are EXTREMELY buggy.  Many times, DrJ seems to
assume that you're on the first column in a line until you type a
character or delete one.

But something is there, and I'll be ironing out the bugs in the underlying
calls before the end of the week.  I'd also be interested in finding out
whether the resize block covers up the numbers on other platforms besides
Mac OS X (what I'm running.)

Let me know, group!

Jim