ProjectExplorer: Move settings structures out of Internal namespace

There is a public exported API that returns these structures,
and different plugins use it, so there is not point in keeping
them inside Internal namespace.

Remove some unused includes.

Change-Id: Ia9d3fc83738c38ae37f04ae0f518ec5d972c9d85
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/projectexplorer/compileoutputwindow.cpp

@@ -6,6 +6,7 @@
 #include "buildmanager.h"
 #include "ioutputparser.h"
 #include "projectexplorer.h"
+#include "projectexplorerconstants.h"
 #include "projectexplorericons.h"
 #include "projectexplorersettings.h"
 #include "showoutputtaskhandler.h"