let-values is better, process-declarations has a macro

let-values now avoids rebinding in sequential forms, which can avoid unused variables in cases like

(let*-values (((a b) ...)
              ((c d) (f a b)))
  ... don't use a and b ...)

process-declarations has a new processing-declaration-specifier macro which makes things a little nicer. It is still unstable. let-values uses process-declarations for its declaration processing now.