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/elfreader.cpp

@@ -30,9 +30,7 @@
 #include "elfreader.h"
 #include "qtcassert.h"
 
-#include <QFile>
 #include <QDir>
-#include <QLibrary>
 #include <QDebug>
 
 namespace Utils {