avcodec: add multi vlc reader

Heavily based and inspired by Christophe's cache branches.

Co-Authored-by: Christophe Gisquet
diff --git a/libavcodec/bitstream.h b/libavcodec/bitstream.h
index b60f0c2..35b7873 100644
--- a/libavcodec/bitstream.h
+++ b/libavcodec/bitstream.h
@@ -102,6 +102,7 @@
 # define bits_decode210     bits_decode210_le
 # define bits_apply_sign    bits_apply_sign_le
 # define bits_read_vlc      bits_read_vlc_le
+# define bits_read_vlc_multi bits_read_vlc_multi_le
 
 #elif defined(BITS_DEFAULT_BE)
 
@@ -130,6 +131,7 @@
 # define bits_decode210     bits_decode210_be
 # define bits_apply_sign    bits_apply_sign_be
 # define bits_read_vlc      bits_read_vlc_be
+# define bits_read_vlc_multi bits_read_vlc_multi_be
 
 #endif