Fix decryption function (HaarigerHarald#154)

Thanks

Author: xibr

youtubeExtractor/src/main/java/at/huber/youtubeExtractor/YouTubeExtractor.java

@@ -82,7 +82,7 @@ public abstract class YouTubeExtractor extends AsyncTask<String, Void, SparseArr
     private static final Pattern patFunction = Pattern.compile("([{; =])([a-zA-Z$_][a-zA-Z0-9$]{0,2})\\(");
 
     private static final Pattern patDecryptionJsFile = Pattern.compile("\\\\/s\\\\/player\\\\/([^\"]+?)\\.js");
-    private static final Pattern patSignatureDecFunction = Pattern.compile("\\b([\\w$]{2})\\s*=\\s*function\\((\\w+)\\)\\{\\s*\\2=\\s*\\2\\.split\\(\"\"\\)\\s*;");
+    private static final Pattern patSignatureDecFunction = Pattern.compile("(?:\\b|[^a-zA-Z0-9$])([a-zA-Z0-9$]{2})\\s*=\\s*function\\(\\s*a\\s*\\)\\s*\\{\\s*a\\s*=\\s*a\\.split\\(\\s*\"\"\\s*\\)");
 
     private static final SparseArray<Format> FORMAT_MAP = new SparseArray<>();