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/environmentmodel.cpp

@@ -32,8 +32,8 @@
 #include <utils/environment.h>
 #include <utils/hostosinfo.h>
 
+#include <QTextDocument> // Qt::escape() in Qt 4
 #include <QFont>
-#include <QTextEdit>
 
 namespace Utils {
 namespace Internal {