Define BackgroundRequestAttribute

This is so that the ConnectInBackground flag can be set on the
QNetworkSession internal to QNAM according to pending requests.

Change-Id: If0cc62f5117ed8febbbda7b7f6de62b11b274258
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
Reviewed-by: Martin Petersson <Martin.Petersson@nokia.com>

src/network/access/qnetworkrequest.cpp

@@ -237,6 +237,14 @@ QT_BEGIN_NAMESPACE
 
     \omitvalue SynchronousRequestAttribute
 
+    \value BackgroundRequestAttribute
+        Type: QVariant::Bool (default: false)
+        Indicates that this is a background transfer, rather than a user initiated
+        transfer. Depending on the platform, background transfers may be subject
+        to different policies.
+        The QNetworkSession ConnectInBackground property will be set according to
+        this attribute.
+
     \value User
         Special type. Additional information can be passed in
         QVariants with types ranging from User to UserMax. The default

src/network/access/qnetworkrequest.h

@@ -87,6 +87,7 @@ public:
         MaximumDownloadBufferSizeAttribute, // internal
         DownloadBufferAttribute, // internal
         SynchronousRequestAttribute, // internal
+        BackgroundRequestAttribute,
 
         User = 1000,
         UserMax = 32767