Turn of *print-pretty* while formatting XML messages

If *print-pretty* is non-nil, net.xml.generator uses pretty p
rinter to indent generated XML nicely, but the output may be
incomplete if other parameters such as *print-level* etc. are
accidentally set.

solr.lisp

@@ -69,8 +69,9 @@
 (defmacro xml->string (&body body)
   (let ((s (gensym)))
     `(with-output-to-string (,s)
-       (with-xml-generation (,s)
-         ,@body))))
+       (let ((*print-pretty* nil))
+         (with-xml-generation (,s)
+           ,@body)))))
 
 ;;;
 ;;; Updating