Remove system locale dependency from timezone code that doesn't need it

Various parts of QTimeZone's code were, for no immediately apparent
reason, conditioned on !defined(QT_NO_SYSTEMLOCALE). All are in any
case conditioned on feature timezone; and none had any obvious
relationship with QLocale::system(). Assume this is a fossil left over
from initial development of timezone support and purge.

[ChangeLog][QtCore][QTimeZone] Some features are now available
whenever feature timezone is enabled, that were previously dependent
on system locale support.

Change-Id: I7f2246e17ace22d2aecc9286295ae522ee2a0f5f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qcore_foundation.mm

@@ -10,7 +10,7 @@
 #include <QtCore/qbytearray.h>
 #include <QtCore/qrect.h>
 
-#if QT_CONFIG(timezone) && !defined(QT_NO_SYSTEMLOCALE)
+#if QT_CONFIG(timezone)
 #include <QtCore/qtimezone.h>
 #include <QtCore/private/qtimezoneprivate_p.h>
 #include <QtCore/private/qcore_mac_p.h>
@@ -466,7 +466,7 @@ NSDate *QDateTime::toNSDate() const
 
 // ----------------------------------------------------------------------------
 
-#if QT_CONFIG(timezone) && !defined(QT_NO_SYSTEMLOCALE)
+#if QT_CONFIG(timezone)
 /*!
     \brief Constructs a new QTimeZone containing a copy of the CFTimeZone \a timeZone.
 

src/corelib/time/qtimezone.cpp

@@ -22,13 +22,6 @@ using namespace Qt::StringLiterals;
 // Create default time zone using appropriate backend
 static QTimeZonePrivate *newBackendTimeZone()
 {
-#ifdef QT_NO_SYSTEMLOCALE
-#if QT_CONFIG(icu)
-    return new QIcuTimeZonePrivate();
-#else
-    return new QUtcTimeZonePrivate();
-#endif
-#else
 #if defined(Q_OS_DARWIN)
     return new QMacTimeZonePrivate();
 #elif defined(Q_OS_ANDROID)
@@ -41,21 +34,13 @@ static QTimeZonePrivate *newBackendTimeZone()
     return new QWinTimeZonePrivate();
 #else
     return new QUtcTimeZonePrivate();
-#endif // System Locales
-#endif // QT_NO_SYSTEMLOCALE
+#endif // Backend selection
 }
 
 // Create named time zone using appropriate backend
 static QTimeZonePrivate *newBackendTimeZone(const QByteArray &ianaId)
 {
     Q_ASSERT(!ianaId.isEmpty());
-#ifdef QT_NO_SYSTEMLOCALE
-#if QT_CONFIG(icu)
-    return new QIcuTimeZonePrivate(ianaId);
-#else
-    return new QUtcTimeZonePrivate(ianaId);
-#endif
-#else
 #if defined(Q_OS_DARWIN)
     return new QMacTimeZonePrivate(ianaId);
 #elif defined(Q_OS_ANDROID)
@@ -68,8 +53,7 @@ static QTimeZonePrivate *newBackendTimeZone(const QByteArray &ianaId)
     return new QWinTimeZonePrivate(ianaId);
 #else
     return new QUtcTimeZonePrivate(ianaId);
-#endif // System Locales
-#endif // QT_NO_SYSTEMLOCALE
+#endif // Backend selection
 }
 
 class QTimeZoneSingleton
@@ -77,10 +61,11 @@ class QTimeZoneSingleton
 public:
     QTimeZoneSingleton() : backend(newBackendTimeZone()) {}
 
-    // The global_tz is the tz to use in static methods such as availableTimeZoneIds() and
-    // isTimeZoneIdAvailable() and to create named IANA time zones.  This is usually the host
-    // system, but may be different if the host resources are insufficient or if
-    // QT_NO_SYSTEMLOCALE is set.  A simple UTC backend is used if no alternative is available.
+    // The global_tz is the tz to use in static methods such as
+    // availableTimeZoneIds() and isTimeZoneIdAvailable() and to create named
+    // IANA time zones. This is usually the host system, but may be different if
+    // the host resources are insufficient. A simple UTC backend is used if no
+    // alternative is available.
     QExplicitlySharedDataPointer<QTimeZonePrivate> backend;
 };
 

src/corelib/time/qtimezone.h

@@ -13,7 +13,7 @@
 
 #include <chrono>
 
-#if QT_CONFIG(timezone) && (defined(Q_OS_DARWIN) || defined(Q_QDOC)) && !defined(QT_NO_SYSTEMLOCALE)
+#if QT_CONFIG(timezone) && (defined(Q_OS_DARWIN) || defined(Q_QDOC))
 Q_FORWARD_DECLARE_CF_TYPE(CFTimeZone);
 Q_FORWARD_DECLARE_OBJC_CLASS(NSTimeZone);
 #endif
@@ -214,7 +214,7 @@ public:
     static QList<QByteArray> windowsIdToIanaIds(const QByteArray &windowsId,
                                                 QLocale::Territory territory);
 
-#  if (defined(Q_OS_DARWIN) || defined(Q_QDOC)) && !defined(QT_NO_SYSTEMLOCALE)
+#  if defined(Q_OS_DARWIN) || defined(Q_QDOC)
     static QTimeZone fromCFTimeZone(CFTimeZoneRef timeZone);
     CFTimeZoneRef toCFTimeZone() const Q_DECL_CF_RETURNS_RETAINED;
     static QTimeZone fromNSTimeZone(const NSTimeZone *timeZone);

src/corelib/time/qtimezoneprivate.cpp

@@ -756,8 +756,11 @@ static bool isEntryInIanaList(QByteArrayView id, QByteArrayView ianaIds)
 }
 
 /*
-    UTC Offset implementation, used when QT_NO_SYSTEMLOCALE set and ICU is not being used,
-    or for QDateTimes with a Qt:Spec of Qt::OffsetFromUtc.
+    UTC Offset backend.
+
+    Always present, based on UTC-offset zones.
+    Complements platform-specific backends.
+    Equivalent to Qt::OffsetFromUtc lightweight time representations.
 */
 
 // Create default UTC time zone