patch applied (ghc): improve break-by-coordinate

[Simon Marlow]

Fri May 18 06:45:56 PDT 2007  Simon Marlow <simonmar at microsoft.com>
  * improve break-by-coordinate
  when setting a breakpoint by coordinate, if there are no spans
  covering the specified coordinate, then we take the leftmost of the
  spans to the right of the coordinate.  This means that ':break c' will
  work if c is not a function, because the first span will be on c's
  right hand side.

    M ./compiler/ghci/InteractiveUI.hs -1 +6