GStreamer: cleanup system includes.

Replaced some linux includes with <private/qcore_unix_p.h> to be more
portable.
Use qt_safe_open() and qt_safe_close() instead of ::open() and
::close().

Task-number: QTBUG-38061
Change-Id: Idb3f50d070ec1701cafba98e79e2e85824653a3a
Reviewed-by: Lisandro Damián Nicanor Pérez Meyer <perezmeyer@gmail.com>
Reviewed-by: Christian Stromme <christian.stromme@digia.com>

src/plugins/gstreamer/mediaplayer/qgstreamerplayerserviceplugin.cpp

@@ -51,20 +51,6 @@
 #include "qgstreamerplayerservice.h"
 #include <private/qgstutils_p.h>
 
-#include <linux/types.h>
-#include <sys/time.h>
-#include <sys/ioctl.h>
-#include <sys/poll.h>
-#include <unistd.h>
-#include <fcntl.h>
-#include <errno.h>
-#include <string.h>
-#include <stdlib.h>
-#include <sys/mman.h>
-#include <linux/videodev2.h>
-#include <gst/gst.h>
-
-
 QMediaService* QGstreamerPlayerServicePlugin::create(const QString &key)
 {
     QGstUtils::initializeGst();