[youtube] Use the first v= argument in the URL

This is according to how youtube handles multiple v= values in one URL.
Before this, it was possible to make a single URL show up differently
 on youtube itself, and if you downloaded/viewed it with youtube-dl/mpv

youtube_dl/extractor/youtube.py

@@ -213,7 +213,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                              |(?:                                             # or the v= param in all its forms
                                  (?:(?:watch|movie)(?:_popup)?(?:\.php)?/?)?  # preceding watch(_popup|.php) or nothing (like /?v=xxxx)
                                  (?:\?|\#!?)                                  # the params delimiter ? or # or #!
-                                 (?:.*?&)?                                    # any other preceding param (like /?s=tuff&v=xxxx)
+                                 (?:.*?&)??                                   # any other preceding param (like /?s=tuff&v=xxxx)
                                  v=
                              )
                          ))
@@ -380,6 +380,23 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 'uploader_id': 'setindia'
             }
         },
+        {
+            'url': 'http://www.youtube.com/watch?v=BaW_jenozKcj&v=UxxajLWwzqY',
+            'note': 'Use the first video ID in the URL',
+            'info_dict': {
+                'id': 'BaW_jenozKc',
+                'ext': 'mp4',
+                'title': 'youtube-dl test video "\'/\\ä↭𝕐',
+                'uploader': 'Philipp Hagemeister',
+                'uploader_id': 'phihag',
+                'upload_date': '20121002',
+                'description': 'test chars:  "\'/\\ä↭𝕐\ntest URL: https://github.com/rg3/youtube-dl/issues/1892\n\nThis is a test video for youtube-dl.\n\nFor more information, contact phihag@phihag.de .',
+                'categories': ['Science & Technology'],
+                'tags': ['youtube-dl'],
+                'like_count': int,
+                'dislike_count': int,
+            }
+        },
         {
             'url': 'http://www.youtube.com/watch?v=a9LDPn-MO4I',
             'note': '256k DASH audio (format 141) via DASH manifest',