Update ICU to 58.1

source/i18n/unicode/ucal.h

Index: source/i18n/unicode/ucal.h
diff --git a/source/i18n/unicode/ucal.h b/source/i18n/unicode/ucal.h
index 36828607099a76e16933992a794cce8a900bc6ee..29c084574e16be667d65bb3c20c59110249f34e8 100644
--- a/source/i18n/unicode/ucal.h
+++ b/source/i18n/unicode/ucal.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) 1996-2015, International Business Machines Corporation and
@@ -423,10 +425,12 @@ enum UCalendarDateFields {
    */
   UCAL_IS_LEAP_MONTH,
 
-  /**
-   * Field count
-   * @stable ICU 2.6
-   */
+    // Do not conditionalize with #ifndef U_HIDE_DEPRECATED_API,
+    // it is needed for layout of Calendar, DateFormat, and other objects
+    /**
+     * One more than the highest normal UCalendarDateFields value.
+     * @deprecated ICU 58 The numeric value may change over time, see ICU ticket #12420.
+     */
   UCAL_FIELD_COUNT,
 
  /**