Add spec suites for conditionals/logic/let/loop/iteration/threading, functions
(definition, application, combinators), and destructuring across let/fn/loop/
doseq/for. Bug caught and fixed: loop* assumed simple-symbol bindings, so
(loop [[a b] [1 2]] ...) errored; it now destructures each binding via
destructure-bind, supporting patterns in loop bindings (and recur). jpm test green.
