eglfs: Check for a valid window handle before attempting to retrieve resources.

In the case of a window that is not yet shown, or destroyed, there
will not be a native handle, and this would crash.

Change-Id: Ib8c1a4490d82654d04073dac240eaa1275cbc1b0
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
Reviewed-by: Andy Nichols <andy.nichols@digia.com>
QPluginLoader: add 'staticPlugins' function

Currently there is no API to extract the meta data
from static plugins. This is needed in e.g QtDeclarative
for loading static module plugins.

This patch moves the 'staticPlugins' function from
QLibraryPrivate into QPluginLoader, and makes it public.
As such, we now also export QStaticPlugin.
Since an application developer cannot do much with raw
metadata, we add a new function
QStaticPlugin::metaData() that returns the QJsonObject
for the plugin. The old metaData function is
renamed 'rawMetaData'.

Change-Id: Idb0bf9ad8ebb13340565512e1998b26e762a357e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>