vp10: extend range for delta Q values.

See issue 1051. 6 bits is fairly arbitrary but at least allows writing
delta Q values that are fairly normal in other codecs. I can extend to
8 if people want full range, although I personally don't have any need
for that.

Change-Id: I0a5a7c3d9b8eb3de4418430ab0e925d4a08cd7a0

vp10/decoder/decodeframe.c

@@ -1125,7 +1125,8 @@ static void setup_loopfilter(struct loopfilter *lf,
 }
 
 static INLINE int read_delta_q(struct vpx_read_bit_buffer *rb) {
-  return vpx_rb_read_bit(rb) ? vpx_rb_read_inv_signed_literal(rb, 4) : 0;
+  return vpx_rb_read_bit(rb) ?
+      vpx_rb_read_inv_signed_literal(rb, CONFIG_MISC_FIXES ? 6 : 4) : 0;
 }
 
 static void setup_quantization(VP10_COMMON *const cm, MACROBLOCKD *const xd,

vp10/encoder/bitstream.c

@@ -733,7 +733,7 @@ static void encode_loopfilter(struct loopfilter *lf,
 static void write_delta_q(struct vpx_write_bit_buffer *wb, int delta_q) {
   if (delta_q != 0) {
     vpx_wb_write_bit(wb, 1);
-    vpx_wb_write_inv_signed_literal(wb, delta_q, 4);
+    vpx_wb_write_inv_signed_literal(wb, delta_q, CONFIG_MISC_FIXES ? 6 : 4);
   } else {
     vpx_wb_write_bit(wb, 0);
   }