Add ifdefs arround native windows code to fix linux build

- There was some native windows code not properly covered by ifdefs.
- handlePushToTalk() is not yet implemented on linux. Add a dummy.

src/blackcore/voice_vatlib.h

@@ -13,7 +13,10 @@
 #include <QMap>
 #include <QSet>
 #include <QString>
+
+#if defined(Q_OS_WIN)
 #include <Windows.h>
+#endif
 
 namespace BlackCore
 {