Use QRecursiveMutex

Instead of deprecated constructor QMutex(QMutex::RecursionMode), use
recommended replacement class QRecursiveMutex.

This deprecation was done only in the KDE branch of Qt, specifically in
https://invent.kde.org/qt/qt/qtbase/-/commit/6d5988831862f081404270bd7fa2f25bc836fdc9.
Since that commit is included in the Qt packaged for some Linux
distributions (e.g. Arch Linux:
https://archlinux.org/packages/extra/x86_64/qt5-base/), it seems worth
respecting this deprecation.

Since QRecursiveMutex was only introduced in Qt 5.14, whereas we need to
support Qt 5.9.5 or better, this involves some #ifdef magic.

src/keys/drivers/YubiKey.cpp

@@ -23,7 +23,6 @@
 #include <QtConcurrent>
 
 YubiKey::YubiKey()
-    : m_interfaces_detect_mutex(QMutex::Recursive)
 {
     int num_interfaces = 0;
 

src/keys/drivers/YubiKey.h

@@ -20,9 +20,15 @@
 #define KEEPASSX_YUBIKEY_H
 
 #include <QHash>
-#include <QMutex>
 #include <QObject>
 #include <QTimer>
+
+#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+#include <QRecursiveMutex>
+#else
+#include <QMutex>
+#endif
+
 #include <botan/secmem.h>
 
 typedef QPair<unsigned int, int> YubiKeySlot;
@@ -85,7 +91,12 @@ class YubiKey : public QObject
     QTimer m_interactionTimer;
     bool m_initialized = false;
     QString m_error;
-    QMutex m_interfaces_detect_mutex;
+
+#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+    QRecursiveMutex m_interfaces_detect_mutex;
+#else
+    QMutex m_interfaces_detect_mutex{QMutex::Recursive};
+#endif
 
     Q_DISABLE_COPY(YubiKey)
 };

src/keys/drivers/YubiKeyInterface.cpp

@@ -19,7 +19,6 @@
 #include "YubiKeyInterface.h"
 
 YubiKeyInterface::YubiKeyInterface()
-    : m_mutex(QMutex::Recursive)
 {
     m_interactionTimer.setSingleShot(true);
     m_interactionTimer.setInterval(300);

src/keys/drivers/YubiKeyInterface.h

@@ -23,6 +23,12 @@
 
 #include <QMultiMap>
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+#include <QRecursiveMutex>
+#else
+#include <QMutex>
+#endif
+
 /**
  * Abstract base class to manage the interfaces to hardware key(s)
  */
@@ -70,7 +76,12 @@ class YubiKeyInterface : public QObject
 
     QMultiMap<unsigned int, QPair<int, QString>> m_foundKeys;
 
-    QMutex m_mutex;
+#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+    QRecursiveMutex m_mutex;
+#else
+    QMutex m_mutex{QMutex::Recursive};
+#endif
+
     QTimer m_interactionTimer;
     bool m_initialized = false;
     QString m_error;