Test page: Change to print margin rulers

[David Forrest]

Hi,

I'd like to suggest that the test page print a couple tails or rulers that go off the printable area, like TeX's test page, so that with the test page we can actually test the printable margins and perhaps change them.

Tex's test page tries for a 1' margin and prints a inch/mm ruler trailing off of each margin into the unprintable area, so you can read directly the  uncenteredness and the actual printable area.