Remove Q_ASSERT from QXmlStream autotest

Report a meaningful fatal error if an unknown token type is encountered
rather than ignoring the error in non-debug builds and reporting an
uninformative message in debug builds.

Change-Id: Id219f3c7cbd4ba3e9875cb81f833720d5d153132
Task-number: QTBUG-17582
Reviewed-by: Rohan McGovern
(cherry picked from commit 1c85fc559ee456a165527d23cb1b7dc237f5504b)

tests/auto/qxmlstream/qc14n.h

@@ -191,9 +191,9 @@ bool QC14N::isDifferent(const QXmlStreamReader &r1,
                    r2.processingInstructionData() == r2.processingInstructionData();
 
         }
+        default:
+            qFatal("%s: Unknown tokenType: %d", Q_FUNC_INFO, static_cast<int>(r1.tokenType()));
+            return false;
     }
-
-    Q_ASSERT_X(false, Q_FUNC_INFO, "This line should never be reached");
-    return false;
 }