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/host-static.ss

@@ -85,6 +85,9 @@
     ((string=? method "floatValue") (->num n))
     ((string=? method "toString") (jolt-num->string n))
     ((string=? method "hashCode") (->num (jnum->exact n)))
+    ;; Double/Float .isNaN / .isInfinite (a non-flonum is neither).
+    ((string=? method "isNaN") (and (flonum? n) (not (= n n))))
+    ((string=? method "isInfinite") (and (flonum? n) (infinite? n)))
     (else (error #f (string-append "No method " method " for number")))))
 
 ;; ---- emit entry points ------------------------------------------------------