Host interop for clojure.data.json: readers, numbers, dates, exceptions

Shaking out clojure.data.json's own test suite (now 134/137):

- Reader.read(char[],off,len) bulk read + PushbackReader.unread(char[],off,len)
  on the string/pushback reader jhosts; instance? java.io.PushbackReader/
  Reader/StringReader (data.json re-wraps a reader unless it's already a
  PushbackReader, so this is load-bearing for repeated reads).
- number protocol dispatch by actual type: a flonum is Double (not Long),
  exact ratio is Ratio, exact integer is Long — value-host-tags split.
- Integer/toHexString|toOctalString|toBinaryString|toString; .isNaN/.isInfinite
  as instance methods on numbers.
- EOFException ctor/class; .isArray on a class-name string.
- dispatch tags for the uuid/bigdec/inst host values so a protocol extended to
  java.util.UUID / java.math.BigDecimal / java.util.Date / java.time.Instant
  reaches its impl; canonical-host-tag strips java.math./java.time.
- instant/zoned/local time values compare = by epoch-ms (two parsed Instants).
- java.time.Instant/parse, java.sql.Date ctor + valueOf, TimeZone/getDefault,
  DateTimeFormatter/ISO_INSTANT.

All runtime .ss (no re-mint). 9 corpus rows certified vs JVM; make test +
shakesmoke green, 0 new divergences.

host/chez/natives-str.ss

@@ -178,6 +178,8 @@
      jolt-nil)
     ((string=? method "subSequence")
      (substring s (jolt->idx (arg 0)) (jolt->idx (arg 1))))
+    ;; Class.isArray over a class-name string: array classes are "[…" (e.g. "[C").
+    ((string=? method "isArray") (and (fx>? (string-length s) 0) (char=? (string-ref s 0) #\[)))
     (else (error #f (string-append "No method " method " for value")))))
 
 ;; --- clojure.core str-* primitives (the substrate clojure.string.clj calls) ---