add timezone support to mod_say_{de,es,ja,nl,th,zh}

add timezone support to mod_say_{de,es,ja,nl,th,zh}

This is nothing more than a shameless copy/paste from another mod_say
module, which already had timezone support. It simply checks if the
timezone variable is set and if it contains a valid timezone, then this
timezone will be used when announcing times/dates.

FS-7048 #resolve