Style Update: Don't discourage nested scope variable declaration

[Warner Losh]

Greetings,

https://reviews.freebsd.org/D25312

This removes the rule that strongly discourages declaring variables in
nested scopes. Times have moved on from the day when this prevented bugs
due to variable shadowing. We have better tools today, and this is more the
style in the rest of the industry. Make style.9 silent about the matter,
leaving it to the discretion of developers and the usual custom of caution
when introducing this to existing files.

Comments? Please go to the review....

Warner