Bug#602094: apt_preferences man page could use some love from a native English speaker

[PJ Weisberg <pjweisberg@gmail.com>]

> - the use of "you": "your biggest nightmare", "your preferences"....

I don't know if there's a style guide regarding the use of 'you', but
I don't like 'they' when the subject is singular.

> - change of meaning: "more problems will arise"-->"more problems can arise"

I'll admit that I changed that because it strained my credulity to
read that there are NO packages in one release that can be used in
another without careful consideration.  But I run Sid on my personal
computer, so maybe I just have below-average carefulness.

-PJ