Allow theming of taxonomy_render_nodes

I want to be able to theme taxonomy_render_nodes so that I can have a table layout on a taxonomy page. The fix is trivial, simply rename taxonomy_render_nodes to theme_taxonomy_render_nodes, and change the one place it is called (in taxonomy_term_page) to a theme('taxonomy_render_nodes', ...) call.

Someone else suggested something similar but more elaborate on the dev mailing list a while back.