Wrap palette code inside CONFIG_PALETTE flag.

This flag was already added to aomedia/master, so bringing it back to
webm/nextgenv2, as part of an effort to get the two codebases in sync.

Change-Id: I2b933a6a160e4210d1411a9e7978149eb8553205
diff --git a/av1/encoder/rd.c b/av1/encoder/rd.c
index ff96714..2b9171f 100644
--- a/av1/encoder/rd.c
+++ b/av1/encoder/rd.c
@@ -90,6 +90,7 @@
     av1_cost_tokens(cpi->switchable_interp_costs[i],
                     fc->switchable_interp_prob[i], av1_switchable_interp_tree);
 
+#if CONFIG_PALETTE
   for (i = 0; i < PALETTE_BLOCK_SIZES; ++i) {
     av1_cost_tokens(cpi->palette_y_size_cost[i],
                     av1_default_palette_y_size_prob[i], av1_palette_size_tree);
@@ -97,7 +98,7 @@
                     av1_default_palette_uv_size_prob[i], av1_palette_size_tree);
   }
 
-  for (i = 0; i < PALETTE_MAX_SIZE - 1; ++i)
+  for (i = 0; i < PALETTE_MAX_SIZE - 1; ++i) {
     for (j = 0; j < PALETTE_COLOR_CONTEXTS; ++j) {
       av1_cost_tokens(cpi->palette_y_color_cost[i][j],
                       av1_default_palette_y_color_prob[i][j],
@@ -106,6 +107,8 @@
                       av1_default_palette_uv_color_prob[i][j],
                       av1_palette_color_tree[i]);
     }
+  }
+#endif  // CONFIG_PALETTE
 
   for (i = 0; i < TX_SIZES - 1; ++i)
     for (j = 0; j < TX_SIZE_CONTEXTS; ++j)