fix some cppcheck warnings

src/kmailtransport/plugins/smtp/smtpjob.cpp

@@ -64,7 +64,7 @@ Q_GLOBAL_STATIC(SessionPool, s_sessionPool)
 class SmtpJobPrivate
 {
 public:
-    SmtpJobPrivate(SmtpJob *parent)
+    explicit SmtpJobPrivate(SmtpJob *parent)
         : q(parent)
     {
     }

src/kmailtransport/precommandjob.cpp

@@ -23,7 +23,7 @@ using namespace MailTransport;
 class PreCommandJobPrivate
 {
 public:
-    PreCommandJobPrivate(PrecommandJob *parent);
+    explicit PreCommandJobPrivate(PrecommandJob *parent);
     QProcess *process = nullptr;
     QString precommand;
     PrecommandJob *const q;

src/kmailtransport/transport.h

@@ -119,7 +119,7 @@ protected:
       Creates a Transport object. Should only be used by TransportManager.
       @param cfgGroup The KConfig group to read its data from.
     */
-    Transport(const QString &cfgGroup);
+    explicit Transport(const QString &cfgGroup);
 
     void usrRead() override;
     bool usrSave() override;

src/kmailtransportakonadi/outboxactions_p.h

@@ -83,7 +83,7 @@ public:
 class DispatchManualTransportAction : public Akonadi::FilterAction
 {
 public:
-    DispatchManualTransportAction(int transportId);
+    explicit DispatchManualTransportAction(int transportId);
 
     ~DispatchManualTransportAction() override;
 

src/kmailtransportakonadi/sentactionattribute.cpp

@@ -22,9 +22,9 @@ public:
 
     Private(const Private &other)
         : QSharedData(other)
+        , mType(other.mType)
+        , mValue(other.mValue)
     {
-        mType = other.mType;
-        mValue = other.mValue;
     }
 
     Type mType = Invalid;