Clean exported headers of the CppTools plugin.

Change-Id: I0144ac33e88980c431c54a6d69bbde28da4b1967
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/cpptools/cpprefactoringchanges.cpp

@@ -39,6 +39,8 @@
 
 #include <utils/qtcassert.h>
 
+#include <QTextDocument>
+
 using namespace CPlusPlus;
 
 namespace CppTools {