Fix build.

'std::function' is defined in header '<functional>'; did you forget to
'#include <functional>'?

--HG--
branch : develop

src/app/valentina/xml/vpattern.cpp

@@ -68,10 +68,7 @@
 #include <QFuture>
 #include <QtConcurrentRun>
 #include <QTimer>
-
-#ifdef Q_CC_MSVC
 #include <functional>
-#endif /* Q_CC_MSVC */
 
 const QString VPattern::AttrReadOnly    = QStringLiteral("readOnly");
 const QString VPattern::AttrLabelPrefix = QStringLiteral("labelPrefix");