[Checkers] Raw types

[Michael Ernst]

Our official line (it wasn't in the manual, so I just added it) is that the
underlying Java program should compile without warnings or errors, and that
there should be no use of raw types.  If a program uses raw types, then I
don't think we should feel obliged to do anything special to handle it --
and anyway, code that isn't generics-correct is likely to have lots of more
basic errors that the programmer should fix before applying a pluggable
type system!  I would like us to focus on the effectiveness of our system
for fully correct generics code, rather than mitigating the problems that
arise from the use of raw types.

                     Thanks,

                    -Mike