KDDateTime: added conversion operator to QVariant

This prevents implicit conversion to base QDateTime and loss of
time-zone information when passing the value as QVariant.

Fixes KDAB#123.

doc/CHANGES_1_8.txt

@@ -20,6 +20,7 @@ Client-side:
 * Rename the missing KDSoapJob::returnHeaders() to KDSoapJob::replyHeaders(), and provide an implementation
 * Make KDSoapClientInterface::soapVersion() const
 * Add lastFaultCode() for error handling after sync calls. Same as lastErrorCode() but it returns a QString rather than an int.
+* Add conversion operator from KDDateTime to QVariant to void implicit conversion to base QDateTime (github issue #123).
 
 Server-side:
 ============

src/KDSoapClient/KDDateTime.cpp

@@ -57,6 +57,11 @@ KDDateTime::~KDDateTime()
 {
 }
 
+KDDateTime::operator QVariant() const
+{
+    return QVariant::fromValue(*this);
+}
+
 QString KDDateTime::timeZone() const
 {
     return d->mTimeZone;

src/KDSoapClient/KDDateTime.h

@@ -50,6 +50,13 @@ class KDSOAP_EXPORT KDDateTime : public QDateTime
     KDDateTime &operator=(const KDDateTime &);
     ~KDDateTime();
 
+    /**
+     * Converts the KDDateTime to QVariant, to avoid implicit conversion
+     * to base QDateTime.
+     * \since 1.8
+     */
+    operator QVariant() const;
+
     /**
      * Returns the time zone set by setTimeZone.
      */