Clean exported headers of the Core plugin.

Change-Id: I26472d568844d5fee62323e01f5c5c12082d5450
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/cpaster/cpasterplugin.cpp

@@ -61,6 +61,7 @@
 #include <QApplication>
 #include <QClipboard>
 #include <QInputDialog>
+#include <QMenu>
 #include <QUrl>
 
 using namespace Core;