Update ICU to 58.1

source/common/unicode/stringtriebuilder.h

Index: source/common/unicode/stringtriebuilder.h
diff --git a/source/common/unicode/stringtriebuilder.h b/source/common/unicode/stringtriebuilder.h
index 04447e543713d1ac9b5c93657fa15073ca436ca2..95cd841a374f83406b5d556e0b50363da7ebef9f 100644
--- a/source/common/unicode/stringtriebuilder.h
+++ b/source/common/unicode/stringtriebuilder.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) 2010-2012,2014, International Business Machines
@@ -184,7 +186,8 @@ protected:
     /** @internal */
     UHashtable *nodes;
 
-#ifndef U_HIDE_INTERNAL_API
+    // Do not conditionalize the following with #ifndef U_HIDE_INTERNAL_API,
+    // it is needed for layout of other objects.
     /** @internal */
     class Node : public UObject {
     public:
@@ -243,6 +246,7 @@ protected:
         int32_t offset;
     };
 
+#ifndef U_HIDE_INTERNAL_API
     // This class should not be overridden because
     // registerFinalValue() compares a stack-allocated FinalValueNode
     // (stack-allocated so that we don't unnecessarily create lots of duplicate nodes)
@@ -258,7 +262,10 @@ protected:
     protected:
         int32_t value;
     };
+#endif  /* U_HIDE_INTERNAL_API */
 
+    // Do not conditionalize the following with #ifndef U_HIDE_INTERNAL_API,
+    // it is needed for layout of other objects.
     /**
      * @internal 
      */
@@ -276,6 +283,7 @@ protected:
         int32_t value;
     };
 
+#ifndef U_HIDE_INTERNAL_API
     /** 
      * @internal 
      */
@@ -289,7 +297,10 @@ protected:
     protected:
         Node *next;
     };
+#endif  /* U_HIDE_INTERNAL_API */
 
+    // Do not conditionalize the following with #ifndef U_HIDE_INTERNAL_API,
+    // it is needed for layout of other objects.
     /**
      * @internal 
      */
@@ -305,6 +316,7 @@ protected:
         Node *next;
     };
 
+#ifndef U_HIDE_INTERNAL_API
     /**
      * @internal 
      */