Adding support for libxml2-2.12.0 and later for Quanta+

Solution to issue #42

Signed-off-by: ormorph <roma251078@mail.ru>
(cherry picked from commit 7ab481cf8b)

quanta/parsers/dtd/dtdparser.cpp

@@ -82,7 +82,8 @@ bool DTDParser::parse(const TQString &targetDir, bool entitiesOnly)
   if( DTD::dtd_ptr == NULL )
   {
     TQString errorStr = i18n("Unknown");
-    xmlErrorPtr errorPtr = xmlGetLastError();
+    // The type used is either xmlErrorPtr or const xmlError*
+    auto errorPtr = xmlGetLastError();
     if (errorPtr != NULL)
     {
       TQString s = TQString::fromLatin1(errorPtr->message);
@@ -98,7 +99,7 @@ bool DTDParser::parse(const TQString &targetDir, bool entitiesOnly)
       if (!s.isEmpty())
         errorStr += "<br>" + s;
       errorStr += TQString("(%1, %2)").arg(errorPtr->line).arg(errorPtr->int2);
-      xmlResetError(errorPtr);
+      xmlResetLastError();
     }
     KMessageBox::error(0, i18n("<qt>Error while parsing the DTD.<br>The error message is:<br><i>%1</i></qt>").arg(errorStr));
     return false;