host interop + deps fixes for running ring-defaults on jolt

Shaken out getting ring-defaults (and its ring-core/anti-forgery/session stack)
to load and serve static resources on jolt. All general fixes, all runtime:

- Class/forName throws a catchable ClassNotFoundException for a class jolt can't
  back (it returned a broken truthy value for any name, and crashed on use). Lets
  the common (try (Class/forName "optional.Dep") (catch ...)) probe libraries use
  to detect an absent dependency work — e.g. ring's joda-time check.
- deps: reconcile native libs (and source roots) in one step, deduped by library
  identity, instead of the ad-hoc distinct at each call site. An app pulling two
  libs that declare the same shared object (libcrypto via both jolt-crypto and
  http-client) now includes and loads it once.
- io: a File answers getProtocol ("file") / getFile so resource-serving
  middleware that expects io/resource to hand back a file: URL works; the
  classloader gains getResources (every source root holding the resource).
- clojure.string/replace accepts a char match/replacement, like the JVM.

JVM-certified corpus rows for the Class/forName and string/replace behavior.

host/chez/natives-str.ss

@@ -303,7 +303,9 @@
 (define (str-replace-all pat repl s)
   (if (jolt-regex? pat)
       (re-replace (regex-t-irx pat) s repl #t)
-      (str-replace-literal s pat repl)))
+      ;; literal match: a char/number match or replacement (str/replace s \a \b)
+      ;; coerces to a string, as on the JVM.
+      (str-replace-literal s (str-needle pat) (str-needle repl))))
 (define (str-replace-literal-first s a b)
   (let ((alen (string-length a)) (i (str-index-of s a 0)))
     (if (fx<? i 0) s
@@ -311,7 +313,7 @@
 (define (str-replace pat repl s)
   (if (jolt-regex? pat)
       (re-replace (regex-t-irx pat) s repl #f)
-      (str-replace-literal-first s pat repl)))
+      (str-replace-literal-first s (str-needle pat) (str-needle repl))))
 
 (def-var! "clojure.core" "str-upper" str-upper)
 (def-var! "clojure.core" "str-lower" str-lower)