Explicitly qualify ICU types with icu:: namespace

It will be required by ICU 61 anyway, see
https://ssl.icu-project.org/repos/icu/trunk/icu4c/readme.html#RecBuild

Change-Id: If7f1330550981fd28eb7eea6329f21e116291cca
Reviewed-on: https://gerrit.libreoffice.org/46740Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>
Reviewed-on: https://gerrit.libreoffice.org/56779
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

lotuswordpro/source/filter/localtime.cxx

@@ -174,7 +174,7 @@ bool LtgLocalTime(long rtime,LtTm& rtm)
 
     if ((rtime > 3 * DAY_SEC)&&(rtime < LONG_MAX - 3 * DAY_SEC))
     {
-        TimeZone* pLocalZone = TimeZone::createDefault();
+        icu::TimeZone* pLocalZone = icu::TimeZone::createDefault();
         long offset = (pLocalZone->getRawOffset())/1000;
         delete pLocalZone;
         long ltime = rtime + offset;