Supply locale to QCollatorPrivate via its constructor

Both places that new'd it were then setting its locale themselves;
they might as well do it tidily by passing it to the constructor.
There's also no need to cleanup() in the constructor; every back-end
is a no-op when collator has its initial value.

Tidied up the class declaration in the process:
 * moved {con,de}structor to be first methods
 * comment on the two methods back-ends provide

Change-Id: I041669637935e68141e002156552af8b475ba36e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qcollator.cpp

@@ -77,9 +77,8 @@ QT_BEGIN_NAMESPACE
     \sa setLocale()
  */
 QCollator::QCollator(const QLocale &locale)
-    : d(new QCollatorPrivate)
+    : d(new QCollatorPrivate(locale))
 {
-    d->locale = locale;
     d->init();
 }
 
@@ -158,8 +157,7 @@ QCollator &QCollator::operator=(const QCollator &other)
 void QCollator::detach()
 {
     if (d->ref.load() != 1) {
-        QCollatorPrivate *x = new QCollatorPrivate;
-        x->locale = d->locale;
+        QCollatorPrivate *x = new QCollatorPrivate(d->locale);
         if (!d->ref.deref())
             delete d;
         d = x;

src/corelib/tools/qcollator_p.h

@@ -104,19 +104,18 @@ public:
 
     CollatorType collator = 0;
 
+    QCollatorPrivate(const QLocale &locale) : locale(locale) {}
+    ~QCollatorPrivate() { cleanup(); }
+
     void clear() {
         cleanup();
         collator = 0;
     }
 
+    // Implemented by each back-end, in its own way:
     void init();
     void cleanup();
 
-    QCollatorPrivate()
-    { cleanup(); }
-
-    ~QCollatorPrivate() { cleanup(); }
-
 private:
     Q_DISABLE_COPY(QCollatorPrivate)
 };