Description:
------------
To confirm, this happens on both 0.9.9 and on SVN latest.

We're sending a request for MoreLikeThis data - 
mlt=true&mlt.fl=metaSimilarity&mlt.boost=true&mlt.count=10&m
lt.mindf=1&mlt.mintf=1&mlt.minwl=1&q=id:(pa
ntone-keyring2)&fq=siteId:bloomsbury AND 
userType:regular_display&terms.sort=count&fl=id - which is 
being handled just fine by your library and by Solr, and is 
returning an XML document (see the attached 
file). 

Unfortunately, SolrQuery::getResponse then throws a warning 
level error of 
	"Error unserializing raw response.", 
which is also thrown when using 
SolrUtils::digestXMLResponse. 

The issue appears to arise when more than one document is 
returned by a MoreLikeThis query - if the 
below result is stripped down to a single Doc element within  
<result name="pantone-keyring2" 
numFound="2693" start="0">, it parses without issue.


Reproduce code:
---------------
Do a MoreLikeThisQuery, or just use digestXMLResponse on

<?xml version="1.0" encoding="UTF-8"?>
<response>

<lst name="responseHeader">
 <int name="status">0</int>
 <int name="QTime">3</int>
 <lst name="params">
  <str name="mlt.minwl">1</str>
  <str name="mlt.boost">true</str>
  <str name="mlt.fl">metaSimilarity</str>
  <str name="indent">on</str>
  <str name="mlt.mintf">1</str>
  <str name="mlt">true</str>
  <str name="wt">xml</str>
  <str name="terms.sort">count</str>
  <str name="version">2.2</str>
  <str name="mlt.mindf">1</str>
  <str name="mlt.count">10</str>
  <str name="fl">id</str>
  <str name="q">id:(pantone-keyring2)</str>
  <str name="fq">siteId:bloomsbury AND userType:regular_display</str>
 </lst>
</lst>
<result name="response" numFound="1" start="0">
 <doc>
  <str name="id">pantone-keyring2</str>
 </doc>
</result>
<lst name="moreLikeThis">
 <result name="pantone-keyring2" numFound="2693" start="0">
  <doc>
	<str name="id">pantone-keyring4</str>
  </doc>
  <doc>
	<str name="id">pantone-keyring3</str>
  </doc>
  <doc>
	<str name="id">pantone-keyring1</str>
  </doc>
  <doc>
	<str name="id">pantone-keyring45</str>
  </doc>
  <doc>
	<str name="id">pantone-keyring6</str>
  </doc>
  <doc>
	<str name="id">pantone-cufflink4</str>
  </doc>
  <doc>
	<str name="id">pantone-cufflink7</str>
  </doc>
  <doc>
	<str name="id">pantone-cufflink5</str>
  </doc>
  <doc>
	<str name="id">pantone-cl-cherry</str>
  </doc>
  <doc>
	<str name="id">pantone-cl-jet</str>
  </doc>
 </result>
</lst>
</response>


Expected result:
----------------
A SolrObject full of delicious data instead of an Error and an 
exception would be nice :)

Actual result:
--------------
As above, failure to unserialize occurs when more than one 
MoreLikeThis document is present.