Update ICU to 58.1

source/common/unicode/bytestrie.h

Index: source/common/unicode/bytestrie.h
diff --git a/source/common/unicode/bytestrie.h b/source/common/unicode/bytestrie.h
index 9c7782740dba2752b1f01264d3977ee615402007..4a30ce1c0428b596ae288bdb480c85cdd1a36ea0 100644
--- a/source/common/unicode/bytestrie.h
+++ b/source/common/unicode/bytestrie.h
@@ -1,3 +1,5 @@
+// Copyright (C) 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
 /*
 *******************************************************************************
 *   Copyright (C) 2010-2012, International Business Machines
@@ -306,7 +308,7 @@ public:
          * @return The NUL-terminated byte sequence for the last successful next().
          * @stable ICU 4.8
          */
-        const StringPiece &getString() const { return sp_; }
+        StringPiece getString() const;
         /**
          * @return The value for the last successful next().
          * @stable ICU 4.8
@@ -325,7 +327,6 @@ public:
         int32_t initialRemainingMatchLength_;
 
         CharString *str_;
-        StringPiece sp_;
         int32_t maxLength_;
         int32_t value_;