ac3enc: change default floor code to 7.

This is to match the value in every (E-)AC-3 file from commercial sources.
It has a negligible effect on audio quality.

Signed-off-by: Mans Rullgard <mans@mansr.com>
(cherry picked from commit 50d7140441)

libavcodec/ac3enc.c

@@ -752,7 +752,7 @@ static void bit_alloc_init(AC3EncodeContext *s)
     s->fast_decay_code = 1;
     s->slow_gain_code  = 1;
     s->db_per_bit_code = 3;
-    s->floor_code      = 4;
+    s->floor_code      = 7;
     for (ch = 0; ch < s->channels; ch++)
         s->fast_gain_code[ch] = 4;
 

tests/ref/acodec/ac3_fixed

@@ -1,2 +1,2 @@
-37e119c644ba0472c079d0e907bf78df *./tests/data/acodec/ac3.rm
+f8eddf3c4e119bcb2aa89a76d7461259 *./tests/data/acodec/ac3.rm
 98751 ./tests/data/acodec/ac3.rm

tests/ref/lavf/rm

@@ -1,2 +1,2 @@
-b97899ef2812cd1c8851dea550e042e4 *./tests/data/lavf/lavf.rm
+d149fc272dfd21fb8908ee21d7b1651b *./tests/data/lavf/lavf.rm
 346706 ./tests/data/lavf/lavf.rm