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/camerabin/camerabincontrol.cpp

@@ -50,18 +50,6 @@
 #include <QtCore/qfile.h>
 #include <QtCore/qmetaobject.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>
-
 QT_BEGIN_NAMESPACE
 
 //#define CAMEABIN_DEBUG 1