Profile HTML Snippets don't respect CIVICRM_UF_WP_BASEPAGE

HTML Snippets for profiles don't respect the CIVICRM_UF_WP_BASEPAGE parameter, which causes HTML Snippets to fail in many Wordpress configurations.

There are several instances of folks encountering this issue on the forums:
http://forum.civicrm.org/index.php?topic=30984.0
http://forum.civicrm.org/index.php?topic=34361.0
http://forum.civicrm.org/index.php?topic=27730.0
http://forum.civicrm.org/index.php?topic=28294.0

The issue lies in CRM/UF/Page/Group.php - search for the comment referencing CRM-3587 and you'll see:
...
elseif ($config->userFramework == 'WordPress')

{ $profile = str_replace('/wp-admin/admin.php', '/index.php', $profile); }

...

Rather than replacing with "/index.php", it should replace with CIVICRM_UF_WP_BASEPAGE.

This is the fix that worked for me, but I feel a bit uncomfortable doing QA on this, because I'm far from a Wordpress expert. If this could be reviewed by a Wordpress person, I'll gladly submit the patch!