qsql: remove empty Result destructors

Change-Id: If7594421fe5a584912e092feb18002f56d6d30f3
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>

src/sql/drivers/ibase/qsql_ibase.cpp

@@ -349,7 +349,6 @@ class QIBaseResult : public QSqlCachedResult
 
 public:
     explicit QIBaseResult(const QIBaseDriver* db);
-    virtual ~QIBaseResult();
 
     bool prepare(const QString &query) Q_DECL_OVERRIDE;
     bool exec() Q_DECL_OVERRIDE;
@@ -901,10 +900,6 @@ QIBaseResult::QIBaseResult(const QIBaseDriver *db)
 {
 }
 
-QIBaseResult::~QIBaseResult()
-{
-}
-
 bool QIBaseResult::prepare(const QString& query)
 {
     Q_D(QIBaseResult);

src/sql/kernel/qsqlcachedresult.cpp

@@ -126,10 +126,6 @@ QSqlCachedResult::QSqlCachedResult(QSqlCachedResultPrivate &d)
 {
 }
 
-QSqlCachedResult::~QSqlCachedResult()
-{
-}
-
 void QSqlCachedResult::init(int colCount)
 {
     Q_D(QSqlCachedResult);

src/sql/kernel/qsqlcachedresult_p.h

@@ -60,8 +60,6 @@ class Q_SQL_EXPORT QSqlCachedResult: public QSqlResult
     Q_DECLARE_PRIVATE(QSqlCachedResult)
 
 public:
-    virtual ~QSqlCachedResult();
-
     typedef QVector<QVariant> ValueCache;
 
 protected: