Cherry pick an upstream cl for host tz detection

source/i18n/unicode/timezone.h

Index: source/i18n/unicode/timezone.h
diff --git a/source/i18n/unicode/timezone.h b/source/i18n/unicode/timezone.h
index fa4f5bf9150345318b542dc6fe3f46ba1b27b91b..c3356c9738a26303525eb4b4b45c76f927415266 100644
--- a/source/i18n/unicode/timezone.h
+++ b/source/i18n/unicode/timezone.h
@@ -1,5 +1,5 @@
 /*************************************************************************
-* Copyright (c) 1997-2014, International Business Machines Corporation
+* Copyright (c) 1997-2015, International Business Machines Corporation
 * and others. All Rights Reserved.
 **************************************************************************
 *
@@ -273,6 +273,23 @@ public:
     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