Fix libvlc_video_get_(height|width) inversion

Both functions remain broken regardless.
Reported-by: Yann Le Hir <yann.lehir@gmail.com>

lib/video.c

@@ -177,18 +177,18 @@ int libvlc_video_get_size( libvlc_media_player_t *p_mi, unsigned num,
 
 int libvlc_video_get_height( libvlc_media_player_t *p_mi )
 {
-    unsigned height, width;
+    unsigned width, height;
 
-    if (libvlc_video_get_size (p_mi, 0, &height, &width))
+    if (libvlc_video_get_size (p_mi, 0, &width, &height))
         return 0;
     return height;
 }
 
 int libvlc_video_get_width( libvlc_media_player_t *p_mi )
 {
-    unsigned height, width;
+    unsigned width, height;
 
-    if (libvlc_video_get_size (p_mi, 0, &height, &width))
+    if (libvlc_video_get_size (p_mi, 0, &width, &height))
         return 0;
     return width;
 }