Update ICU to 58.1

source/common/unicode/bytestriebuilder.h

Index: source/common/unicode/bytestriebuilder.h
diff --git a/source/common/unicode/bytestriebuilder.h b/source/common/unicode/bytestriebuilder.h
index d00ab9b3b0947d0d05c8935f98efe15073da6218..fe96887d511d7e3deacdaf4ab2dcb27e56bf39cf 100644
--- a/source/common/unicode/bytestriebuilder.h
+++ b/source/common/unicode/bytestriebuilder.h
@@ -1,6 +1,8 @@
+// Copyright (C) 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
 /*
 *******************************************************************************
-*   Copyright (C) 2010-2014, International Business Machines
+*   Copyright (C) 2010-2016, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 *******************************************************************************
 *   file name:  bytestriebuilder.h
@@ -29,7 +31,6 @@ U_NAMESPACE_BEGIN
 
 class BytesTrieElement;
 class CharString;
-
 /**
  * Builder class for BytesTrie.
  *
@@ -65,7 +66,7 @@ public:
      * @return *this
      * @stable ICU 4.8
      */
-    BytesTrieBuilder &add(const StringPiece &s, int32_t value, UErrorCode &errorCode);
+    BytesTrieBuilder &add(StringPiece s, int32_t value, UErrorCode &errorCode);
 
     /**
      * Builds a BytesTrie for the add()ed data.
@@ -152,7 +153,8 @@ private:
     private:
         const char *s;
     };
-
+    
+    // don't use #ifndef U_HIDE_INTERNAL_API with private class members or virtual methods.
     virtual Node *createLinearMatchNode(int32_t i, int32_t byteIndex, int32_t length,
                                         Node *nextNode) const;