fix CLucene build for MSVC 2013

Commit qtbase/9f0e5d00ab51cc7c0dc87c8d72f48c4e6edaf120 added the
/Zc:strictStrings compiler option to MSVC 2013 builds.
We're circumventing the problem by throwing const_casts into the code.

Change-Id: I45cc647b780f834b756caed92c4d6f9a50a53664
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>

src/assistant/3rdparty/clucene/src/CLucene/StdHeader.cpp

@@ -24,8 +24,10 @@
 
 CL_NS_USE(util)
 
-TCHAR* _LUCENE_BLANK_STRING = _T("");
-char* _LUCENE_BLANK_ASTRING = "";
+const TCHAR *_CONST_LUCENE_BLANK_STRING = _T("");
+const char *_CONST_LUCENE_BLANK_ASTRING = "";
+TCHAR* _LUCENE_BLANK_STRING = const_cast<TCHAR *>(_CONST_LUCENE_BLANK_STRING);
+char* _LUCENE_BLANK_ASTRING = const_cast<char *>(_CONST_LUCENE_BLANK_ASTRING);
 
 #ifndef Q_CC_MIPS
 #if defined(_LUCENE_THREADMUTEX_USINGDEFAULT)