allow conformsToRole(...) to override compiled-in roles.
Accessors for Array and Pointer.
Expressions are dereferenceable if they bear pointer types.
Pass arguments to Variable->declaration on to Declare constructor.
Allow test.sh to test other scripts.
Expression will generate '&x' for any Addressable expression. Function->pointer calls through to Expression::pointer.
Codify callability (Expr is callable if it's a func or funcptr), allowing expressions to be called like functions.