Moved class FileUtils out of Internal namespace

...because it is being exported.

Change-Id: If2892f8455b7c7fb9a78a8cde27642901ae4bf3a
Reviewed-on: http://codereview.qt.nokia.com/3676
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

src/plugins/coreplugin/fileutils.cpp

@@ -52,7 +52,7 @@
 #endif
 #endif
 
-using namespace Core::Internal;
+using namespace Core;
 
 #if !defined(Q_OS_WIN) && !defined(Q_OS_MAC)
 // Show error with option to open settings.