Simplify QTzTimeZonePrivate implementation

- Don't init m_icu with 0. It's a QSharedDataPointer, which inits to
  nullptr anyway.
- The copy ctor didn't do anything out of the ordinary, so = default it.
  It's also only used in the implementation of clone(), so make it private.

Removes three #if QT_CONFIG blocks.

We can't use ctor delegation here, because systemTimeZoneId() is a
virtual function.

Change-Id: I2cd06c3349686b6f21c897acb5c12185a36d5b9f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qtimezoneprivate_p.h

@@ -287,12 +287,12 @@ Q_DECL_CONSTEXPR inline bool operator!=(const QTzTransitionRule &lhs, const QTzT
 
 class Q_AUTOTEST_EXPORT QTzTimeZonePrivate Q_DECL_FINAL : public QTimeZonePrivate
 {
+    QTzTimeZonePrivate(const QTzTimeZonePrivate &) = default;
 public:
     // Create default time zone
     QTzTimeZonePrivate();
     // Create named time zone
     QTzTimeZonePrivate(const QByteArray &ianaId);
-    QTzTimeZonePrivate(const QTzTimeZonePrivate &other);
     ~QTzTimeZonePrivate();
 
     QTimeZonePrivate *clone() Q_DECL_OVERRIDE;

src/corelib/tools/qtimezoneprivate_tz.cpp

@@ -615,32 +615,16 @@ static QVector<QTimeZonePrivate::Data> calculatePosixTransitions(const QByteArra
 
 // Create the system default time zone
 QTzTimeZonePrivate::QTzTimeZonePrivate()
-#if QT_CONFIG(icu)
-    : m_icu(0)
-#endif
 {
     init(systemTimeZoneId());
 }
 
 // Create a named time zone
 QTzTimeZonePrivate::QTzTimeZonePrivate(const QByteArray &ianaId)
-#if QT_CONFIG(icu)
-    : m_icu(0)
-#endif
 {
     init(ianaId);
 }
 
-QTzTimeZonePrivate::QTzTimeZonePrivate(const QTzTimeZonePrivate &other)
-                  : QTimeZonePrivate(other), m_tranTimes(other.m_tranTimes),
-                    m_tranRules(other.m_tranRules), m_abbreviations(other.m_abbreviations),
-#if QT_CONFIG(icu)
-                    m_icu(other.m_icu),
-#endif
-                    m_posixRule(other.m_posixRule)
-{
-}
-
 QTzTimeZonePrivate::~QTzTimeZonePrivate()
 {
 }