Add QProcess check in msgpackiodevice dtor

This uses a dynamic cast for casting this to a QProcess and calls
QProcess::terminate() to try and softly shut it down, waiting at most
100ms for the process.

src/msgpackiodevice.cpp

@@ -1,5 +1,6 @@
 #include <QAbstractSocket>
 #include <QSocketNotifier>
+#include <QProcess>
 
 // read/write
 #ifdef _WIN32
@@ -72,6 +73,16 @@ MsgpackIODevice::~MsgpackIODevice()
 {
 	//msgpack_packer_destroy(&m_pk);
 	msgpack_unpacker_destroy(&m_uk);
+
+	// If the device is backed by a QProcess then the QProcess dtor will
+	// be used, but its default behaviour is too aggressive (SIGKILL). Try
+	// to softly bring it down here first.
+	QProcess* p = qobject_cast<QProcess*>(m_dev);
+	if (p) {
+		p->terminate();
+		bool fin = p->waitForFinished(100);
+		qDebug() << "Terminating QProcess device" << fin;
+	}
 }
 
 bool MsgpackIODevice::isOpen()