Fix #2885: convert number entity to character

pkgs/racket-test/tests/xml/num-entity.rkt

@@ -0,0 +1,15 @@
+#lang racket/base
+(require xml)
+
+(module+ test
+  (require rackunit)
+
+  (define ex #<<EOF
+<?xml version="1.0"?>
+<blah foo="1 &amp;&#13;&#10;2" />
+EOF
+    )
+
+  (check-equal?
+   (xml->xexpr (document-element (read-xml (open-input-string ex))))
+   '(blah ((foo "1 &\r\n2")))))

racket/collects/xml/private/reader.rkt

@@ -180,7 +180,7 @@
     [(gt) ">"]
     [(quot) "\""]
     [(apos) "'"]
-    [else #f]))
+    [else (and (number? name) (string (integer->char name)))]))
 
 (define-struct (EOF source) ())