Accept nooped plurals in wp_generate_tag_cloud() / wp_tag_cloud().

Renders topic_count_text_callback more or less obsolete. It can still be used, but passing a plural is easier.

fixes #27262. see #7989, #14424.


git-svn-id: https://develop.svn.wordpress.org/trunk@27376 602fd350-edb4-49c9-b593-d223f7449a82