CppTools: Fix compile for gcc 4.9

Seems gcc 4.9 cannot handle forward declared classes in uniqe_ptr
correctly. Broke with 7666db896d.

Change-Id: Ib7e7d9d22e5b0a1d50a107202108ec2937e0a284
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/plugins/cpptools/cppmodelmanager.h

@@ -34,6 +34,8 @@
 #include "stringtable.h"
 
 #include <cplusplus/cppmodelmanagerbase.h>
+#include <coreplugin/find/ifindfilter.h>
+#include <coreplugin/locator/ilocatorfilter.h>
 
 #include <QFuture>
 #include <QObject>
@@ -42,8 +44,6 @@
 namespace Core {
 class IDocument;
 class IEditor;
-class ILocatorFilter;
-class IFindFilter;
 }
 namespace CPlusPlus { class LookupContext; }
 namespace ProjectExplorer { class Project; }