Remove circular dependency in testlib logging

Remove one of the circular dependencies between QPlainTestLogger and
QTestLog by directly checking whether we're writing to stdout rather
than inferring the same by examining whether the output file name is
null.

Change-Id: I798288482c9e2e071e17a8622e8a8f8d5016dc7e
Reviewed-on: http://codereview.qt.nokia.com/4052
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>

src/testlib/qabstracttestlogger_p.h

@@ -98,7 +98,7 @@ public:
 
     void outputString(const char *msg);
 
-private:
+protected:
     FILE *stream;
 };
 

src/testlib/qplaintestlogger.cpp

@@ -211,7 +211,7 @@ void QPlainTestLogger::outputMessage(const char *str)
         OutputDebugString((wchar_t*)tmp.utf16());
         strUtf16.remove(0, maxOutputLength);
     } while (!strUtf16.isEmpty());
-    if (QTestLog::outputFileName())
+    if (stream != stdout)
 #elif defined(Q_OS_WIN)
     EnterCriticalSection(&QTest::outputCriticalSection);
     // OutputDebugString is not threadsafe