Show correct export date range for pages. The query should use provided...

Show correct export date range for pages. The query should use provided $post_type instead of always 'post'. Props sorich87. Fixes #19312.


git-svn-id: https://core.svn.wordpress.org/trunk@19626 1a063a9b-81f0-0310-95a4-ce76da25c4cd