In libs/ add some more explicit keywords where useful

libs/db/tableviewcolumn.h

@@ -41,7 +41,7 @@ public:
 
     /*! Not db-aware ctor. if \a owner is true, the field \a will be owned by this column,
      so you shouldn't care about destroying this field. */
-    TableViewColumn(Field& f, bool owner = false);
+    explicit TableViewColumn(Field& f, bool owner = false);
 
     /*! Not db-aware, convenience ctor, like above. The field is created using specified parameters that are
      equal to these accepted by KexiDB::Field ctor. The column will be the owner

libs/db/validator.h

@@ -45,7 +45,7 @@ class CALLIGRADB_EXPORT Validator : public QValidator
 public:
     enum Result { Error = 0, Ok = 1, Warning = 2 };
 
-    Validator(QObject * parent = 0);
+    explicit Validator(QObject * parent = 0);
 
     virtual ~Validator();
 

libs/kopageapp/widgets/KoPABackgroundFillWidget.h

@@ -31,7 +31,7 @@ class KoPAViewBase;
 class KOPAGEAPP_EXPORT KoPABackgroundFillWidget : public KoFillConfigWidget
 {
 public:
-    KoPABackgroundFillWidget(QWidget *parent);
+    explicit KoPABackgroundFillWidget(QWidget *parent);
 
     void setView(KoPAViewBase *view);
 

libs/main/KoApplication.h

@@ -57,7 +57,7 @@ public:
      *
      * @param nativeMimeType: the nativeMimeType of the calligra application
      */
-    KoApplication(const QByteArray &nativeMimeType);
+    explicit KoApplication(const QByteArray &nativeMimeType);
 
     /**
      *  Destructor.

libs/main/KoPrintingDialog_p.h

@@ -44,7 +44,7 @@
 
 class KoPrintingDialogPrivate {
 public:
-    KoPrintingDialogPrivate(KoPrintingDialog *dia)
+    explicit KoPrintingDialogPrivate(KoPrintingDialog *dia)
         : parent(dia),
           stop(true),
           shapeManager(0),