fixed: size of OAI set displayed incorrectly

In the WIS community there is a convention that the size of OAI set is
included in ListSet response.

http://www.wis-jma.go.jp/meta/oaiprovider.jsp?verb=ListSets

Until last week there was an problem that the size of WIS-GISC-TOKYO is not
displayed correctly. It is now fixed and it returns reliable number.

The documentation at http://www.wis-jma.go.jp/cms/metadata/oai-pmh/ uses the
ListSets internally, and hence fixed accordingly.