Improve status bar search

[tvalusek]

The search for a status bar, as used by the reportStatusLine script, currently fails in many cases, including Mozilla products. This search should be improved so that it works in as many cases as possible.

[jteh]

There are two possibilities:

• Just search the hierarchy for an object with a role of status bar.
  • This could be quite slow, but we need to investigate this.
  • If more than one status bar, which do we choose? Probably just the first.
• We might be able to try getting the object at the coordinates of the bottom of the foreground window. From there, we can move up the hierarchy looking for a status bar.
  • What coordinates do we use: bottom left of window?
  • The status bar may not be at the bottom of the window.
  • How often would this work?

[jteh]

Implemented in r1875. I went for the second approach above; i.e. using the object at the bottom left in terms of screen coordinates. Please comment if reportStatusLine now fails in any cases where it used to work. Note that this still won't work in applications that do not expose accessible status bars; e.g. Microsoft Office 2000.