test(spec): macros, reader, host-interop, namespaces — fix def-doc, resolve, %&

Final spec areas. Bugs caught and fixed:
- (def name docstring value) used the docstring as the value; now the 3-arg
  docstring form binds the value and records :doc meta
- resolve was a nil stub; now a special form resolving a symbol to its var
  (nil if unresolved). Added find-ns (non-creating lookup) and ns-name.
- in-ns didn't evaluate its arg, so (in-ns 'foo) failed; now evaluates it per
  Clojure (the integration test's unquoted form updated to the quoted idiom)
- #(... %& ...) built %& as a positional param instead of a & rest param;
  now emits (fn* [... & gen] ...) so %& captures the rest

Full public-API spec layer now in place. conformance 218/218, jpm test green.

test/integration/namespace-test.janet

@@ -10,14 +10,14 @@
 
 (print "1: in-ns...")
 (let [ctx (make-ctx)]
-  (def form (parse-string "(in-ns my.app)"))
+  (def form (parse-string "(in-ns 'my.app)"))
   (eval-form ctx @{} form)
   (assert (= "my.app" (ctx-current-ns ctx)) "in-ns switches namespace"))
 (print "  passed")
 
 (print "2: def in different namespace...")
 (let [ctx (make-ctx)]
-  (eval-form ctx @{} (parse-string "(in-ns my.app)"))
+  (eval-form ctx @{} (parse-string "(in-ns 'my.app)"))
   (eval-form ctx @{} (parse-string "(def x 42)"))
   (let [ns (ctx-find-ns ctx "my.app")
         v (ns-find ns "x")]