Suggested fix lp:#213718 (bazaar pager)

[Richard Wilbur]

@Joshua:  Thanks for clearing the air regarding stacked branches.
Thank you also for the link to the blog post--interesting and
informative reading.  I'm glad for the good architectural choices of
the past.

@Daniel:  My initial inclination would be to make pager-threshold
configurable rather than hard coding it.  We could use 23 for the
default value.

Self-adjusting pager-threshold would be another interesting direction.
What about querying to see if we are on a terminal and then, if so,
querying how tall the terminal is?

I would also vote for BZR_PAGER environment variable support to
provide a more consistent public interface.

Later,
Richard