[Groff] Getting rid of -r bell

[Eric S. Raymond]

We can get rid of -r bell if we want. 

1. We define .SC unconditionally.  

2. It's a section-header macro, so it's going to be used very early in the
document if it's used at all.

3. Calling .SC sets the bell register, enabling the Bell Labs meaings
of .P1/.P2/.UC and disabling the Berkeley ones.

Too dodgy?
-- 
                <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>