avdevice/x11grab: rename the "w" Window to "root" in paint_mouse_pointer

This specifies better the meaning of the variable, and is also in
preparation of a subsequent change which will introduce a temporary
Window variable for which "w" is an good name.
Signed-off-by: Antonio Ospite <ao2@ao2.it>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavdevice/x11grab.c

@@ -389,7 +389,7 @@ static void paint_mouse_pointer(XImage *image, AVFormatContext *s1)
      * Anyone who performs further investigation of the xlib API likely risks
      * permanent brain damage. */
     uint8_t *pix = image->data;
-    Window w;
+    Window root;
     XSetWindowAttributes attr;
 
     /* Code doesn't currently support 16-bit or PAL8 */
@@ -398,9 +398,9 @@ static void paint_mouse_pointer(XImage *image, AVFormatContext *s1)
 
     if (!s->c)
         s->c = XCreateFontCursor(dpy, XC_left_ptr);
-    w = DefaultRootWindow(dpy);
+    root = DefaultRootWindow(dpy);
     attr.cursor = s->c;
-    XChangeWindowAttributes(dpy, w, CWCursor, &attr);
+    XChangeWindowAttributes(dpy, root, CWCursor, &attr);
 
     xcim = XFixesGetCursorImage(dpy);
     if (!xcim) {