x11: Fix x11grab BadCursor

Fixes Ticket1738

Based-on: A fix found in a perl module (http://ffmpeg.org/pipermail/ffmpeg-user/2012-August/008804.html)
Reviewed-by: Clemens Fruhwirth <clemens@endorphin.org>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavdevice/x11grab.c

@@ -43,6 +43,7 @@
 #include "libavutil/parseutils.h"
 #include "libavutil/time.h"
 #include <time.h>
+#include <X11/cursorfont.h>
 #include <X11/X.h>
 #include <X11/Xlib.h>
 #include <X11/Xlibint.h>
@@ -357,6 +358,12 @@ paint_mouse_pointer(XImage *image, struct x11grab *s)
     if (image->bits_per_pixel != 24 && image->bits_per_pixel != 32)
         return;
 
+    Cursor c = XCreateFontCursor(dpy, XC_left_ptr);
+    Window w = DefaultRootWindow(dpy);
+    XSetWindowAttributes attr;
+    attr.cursor = c;
+    XChangeWindowAttributes(dpy, w, CWCursor, &attr);
+
     xcim = XFixesGetCursorImage(dpy);
 
     x = xcim->x - xcim->xhot;