ruby: restrict Address to being a type and not a variable name

ruby: restrict Address to being a type and not a variable name
Change all occurrances of Address as a variable name to instead use Addr.
Address is an allowed name in slicc even when Address is also being used as a
type, leading to declarations of "Address Address". While this works, it
prevents adding another field of type Address because the compiler then thinks
Address is a variable name, not type.

Committed by: Nilay Vaish <nilay@cs.wisc.edu>