Fix regression with QSettings patch

The plugin loader is used without QCoreApplication.
This fixes 31ef8fa6abc2ea23c6f0a996b36494d88aafb0b5
(cherry picked from commit 988871dabf3c949ffc71d126131281a3ae641ebf)

src/corelib/kernel/qcoreapplication.cpp

@@ -270,7 +270,16 @@ bool QCoreApplicationPrivate::is_app_closing = false;
 Q_CORE_EXPORT bool qt_locale_initialized = false;
 
 
-QSettings *QCoreApplicationPrivate::trolltechConf = 0;
+/*
+  Create an instance of Trolltech.conf. This ensures that the settings will not
+  be thrown out of QSetting's cache for unused settings.
+  */
+Q_GLOBAL_STATIC_WITH_ARGS(QSettings, trolltechConf, (QSettings::UserScope, QLatin1String("Trolltech")))
+
+QSettings *QCoreApplicationPrivate::trolltechConf()
+{
+    return ::trolltechConf();
+}
 
 Q_CORE_EXPORT uint qGlobalPostedEventsCount()
 {
@@ -373,9 +382,6 @@ QCoreApplicationPrivate::~QCoreApplicationPrivate()
         threadData->postEventList.recursion = 0;
         threadData->quitNow = false;
     }
-
-    delete trolltechConf;
-    trolltechConf = 0;
 }
 
 void QCoreApplicationPrivate::createEventDispatcher()
@@ -697,13 +703,6 @@ void QCoreApplication::init()
     }
 #endif
 
-
-    /*
-      Create an instance of Trolltech.conf. This ensures that the settings will not
-      be thrown out of QSetting's cache for unused settings.
-      */
-    d->trolltechConf = new QSettings(QSettings::UserScope, QLatin1String("Trolltech"));
-
     qt_startup_hook();
 }
 

src/corelib/kernel/qcoreapplication_p.h

@@ -142,7 +142,7 @@ public:
 #if defined(QT3_SUPPORT)
     static bool useQt3Support;
 #endif
-    static QSettings *trolltechConf;
+    static QSettings *trolltechConf();
 };
 
 QT_END_NAMESPACE

src/corelib/plugin/qlibrary.cpp

@@ -706,7 +706,7 @@ bool QLibraryPrivate::isPlugin(QSettings *settings)
     QStringList reg;
 #ifndef QT_NO_SETTINGS
     if (!settings) {
-        settings = QCoreApplicationPrivate::trolltechConf;
+        settings = QCoreApplicationPrivate::trolltechConf();
     }
     reg = settings->value(regkey).toStringList();
 #endif