Cherry pick an upstream cl for host tz detection

source/i18n/unicode/timezone.h

 /*************************************************************************
-* Copyright (c) 1997-2014, International Business Machines Corporation
+* Copyright (c) 1997-2015, International Business Machines Corporation
 * and others. All Rights Reserved.
 **************************************************************************
 *
 * File TIMEZONE.H
 *
 * Modification History:
 *
 *   Date        Name        Description
 *   04/21/97    aliu        Overhauled header.
 *   07/09/97    helena      Changed createInstance to createDefault.
@@ skipping 253 matching lines @@
      * returned by <code>countEquivalentIDs(id)</code>
      * @return the ID of the index-th zone in the equivalency group
      * containing 'id', or an empty string if 'id' is not a valid
      * system ID or 'index' is out of range
      * @see #countEquivalentIDs
      * @stable ICU 2.0
      */
     static const UnicodeString U_EXPORT2 getEquivalentID(const UnicodeString& id,
                                                int32_t index);
 
+#ifndef U_HIDE_DRAFT_API
+    /**
+     * Creates an instance of TimeZone detected from the current host
+     * system configuration. Note that ICU4C does not change the default
+     * time zone unless TimeZone::adoptDefault(TimeZone*) or
+     * TimeZone::setDefault(const TimeZone&) is explicitly called by a
+     * user. This method does not update the current ICU's default,
+     * and may return a different TimeZone from the one returned by
+     * TimeZone::createDefault().
+     *
+     * @return  A new instance of TimeZone detected from the current host system
+     *          configuration.
+     * @draft ICU 55
+     */
+    static TimeZone* U_EXPORT2 detectHostTimeZone();
+#endif
+
     /**
      * Creates a new copy of the default TimeZone for this host. Unless the default time
      * zone has already been set using adoptDefault() or setDefault(), the default is
      * determined by querying the system using methods in TPlatformUtilities. If the
      * system routines fail, or if they specify a TimeZone or TimeZone offset which is not
      * recognized, the TimeZone indicated by the ID kLastResortID is instantiated
      * and made the default.
      *
      * @return   A default TimeZone. Clients are responsible for deleting the time zone
      *           object returned.
@@ skipping 653 matching lines @@
 TimeZone::setID(const UnicodeString& ID)
 {
     fID = ID;
 }
 U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
 #endif //_TIMEZONE
 //eof