4xm: fix invalid array indexing

Indexing outside arrays is invalid and breaks with gcc 4.8.
Signed-off-by: Mans Rullgard <mans@mansr.com>

libavcodec/4xm.c

@@ -240,15 +240,18 @@ static void idct(DCTELEM block[64])
 
 static av_cold void init_vlcs(FourXContext *f)
 {
-    static VLC_TYPE table[8][32][2];
-    int i;
-
-    for (i = 0; i < 8; i++) {
-        block_type_vlc[0][i].table           = table[i];
-        block_type_vlc[0][i].table_allocated = 32;
-        init_vlc(&block_type_vlc[0][i], BLOCK_TYPE_VLC_BITS, 7,
-                 &block_type_tab[0][i][0][1], 2, 1,
-                 &block_type_tab[0][i][0][0], 2, 1, INIT_VLC_USE_NEW_STATIC);
+    static VLC_TYPE table[2][4][32][2];
+    int i, j;
+
+    for (i = 0; i < 2; i++) {
+        for (j = 0; j < 4; j++) {
+            block_type_vlc[i][j].table           = table[i][j];
+            block_type_vlc[i][j].table_allocated = 32;
+            init_vlc(&block_type_vlc[i][j], BLOCK_TYPE_VLC_BITS, 7,
+                     &block_type_tab[i][j][0][1], 2, 1,
+                     &block_type_tab[i][j][0][0], 2, 1,
+                     INIT_VLC_USE_NEW_STATIC);
+        }
     }
 }