Encrypted sig 87 broken again (fixes #1200)

youtube_dl/extractor/youtube.py

@@ -338,7 +338,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
         elif len(s) == 88:
             return s[48] + s[81:67:-1] + s[82] + s[66:62:-1] + s[85] + s[61:48:-1] + s[67] + s[47:12:-1] + s[3] + s[11:3:-1] + s[2] + s[12]
         elif len(s) == 87:
-            return s[4:23] + s[86] + s[24:85]
+            return s[83:53:-1] + s[3] + s[52:40:-1] + s[86] + s[39:10:-1] + s[0] + s[9:3:-1] + s[53]
         elif len(s) == 86:
             return s[83:85] + s[26] + s[79:46:-1] + s[85] + s[45:36:-1] + s[30] + s[35:30:-1] + s[46] + s[29:26:-1] + s[82] + s[25:1:-1]
         elif len(s) == 85: