CppTools: Fix compile with gcc 4.7.3

Change-Id: I6a6f0a8ab065fb2c02373165a4b43d76f039d1f3
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>

src/plugins/cpptools/cpptoolsreuse.cpp

@@ -292,7 +292,7 @@ bool skipFileDueToSizeLimit(const QFileInfo &fileInfo, int limitInMB)
 Utils::FileNameList modifiedFiles()
 {
     Utils::FileNameList files = Utils::transform(Core::DocumentManager::modifiedDocuments(),
-                                                 &Core::IDocument::filePath);
+                                                 [](Core::IDocument *d) -> Utils::FileName { return d->filePath(); });
     return Utils::filteredUnique(files);
 }