blogtitle and realname are incompatible

Issue Summary

The blogtitle and realname modules don't play well together. With both enabled, when I go to e.g. blog/3, I get

Fatal error: Call to undefined function blog_page_user() in /home/andrex/html/tealtoes.org/trunk/sites/all/modules/realname/realname.module on line 186

I've posted a full description of the cause of this problem at #566610: blogtitle and realname are incompatible. For realname, what it comes down to is that when the blogtitle module is present, realname should do one of the following:

1. Call blogtitle_blog_page_user() instead of blog_page_user(), in realname_blog_page().
2. Not intercept the user blog page at all. This should be fine as long as blogtitle properly uses $account->realname instead of $account->name to create the page title. I've submitted a patch at #566610: blogtitle and realname are incompatible to do this. However, if the blogtitle module were later disabled, then I'm not sure that realname would have a way to do its work.

I'm attaching a patch that implements #1 above. It's very simple, but I'm not sure it's the best approach, since it calls blogtitle_blog_page_user(), which is internal to blogtitle. It does fix the error, though.

Thanks,
Andrew.