Fix build for Qt 5 configured without -developer-build

This patch reverts 2b0c1fb376 and
affd4b9ce1

Change-Id: I65daf80a0e510f4103c2f2714a3ee583207e53d0
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/coreplugin/coreplugin.pro

@@ -6,7 +6,7 @@ QT += network \
     sql
 
 greaterThan(QT_MAJOR_VERSION, 4) {
-    QT += help printsupport core-private
+    QT += help printsupport
 } else {
     CONFIG += help
 }

src/plugins/coreplugin/fileutils.cpp

@@ -45,8 +45,6 @@
 
 #if QT_VERSION < 0x050000
 #include <QAbstractFileEngine>
-#else
-#include <private/qabstractfileengine_p.h>
 #endif
 
 #ifndef Q_OS_WIN
@@ -195,9 +193,13 @@ void FileUtils::removeFile(const QString &filePath, bool deleteFromFS)
 static inline bool fileSystemRenameFile(const QString &orgFilePath,
                                         const QString &newFilePath)
 {
+#if QT_VERSION < 0x050000
     QAbstractFileEngine *fileEngine = QAbstractFileEngine::create(orgFilePath); // Due to QTBUG-3570
     if (!fileEngine->caseSensitive() && orgFilePath.compare(newFilePath, Qt::CaseInsensitive) == 0)
         return fileEngine->rename(newFilePath);
+#endif
+    // QTBUG-3570 is also valid for Qt 5 but QAbstractFileEngine is now in a private header file and
+    // the symbol is not exported.
     return QFile::rename(orgFilePath, newFilePath);
 }