Clean headers in Utils.

Forward-declare QGraphicsOpacityEffect in DetailsButton,
QProcessEnvironment in Environment, QFileInfo in fileutils,
QUrl in IWelcomePage, FancyLineEdit in PathChooser and
remove unneeded headers.

Change-Id: I7d5f273530dd2059bbdaf0899f0a3bc7e49e8482
Reviewed-by: hjk <hjk121@nokiamail.com>

src/libs/utils/fileutils.h

@@ -33,9 +33,7 @@
 #include "utils_global.h"
 
 #include <QCoreApplication>
-#include <QIODevice>
 #include <QXmlStreamWriter> // Mac.
-#include <QFileInfo>
 #include <QMetaType>
 
 QT_BEGIN_NAMESPACE
@@ -45,6 +43,8 @@ class QWidget;
 class QTextStream;
 class QDataStream;
 class QDateTime;
+class QFileInfo;
+class QDir;
 QT_END_NAMESPACE
 
 namespace Utils {