Audit home_url() vs. site_url() usage.  Fixes #2549.

Also replace instances of site_url() concatenation with native BP functions.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@6975 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Use wp_lostpassword_url() instead of concatenated site_url().

git-svn-id: https://buddypress.svn.wordpress.org/trunk@6976 cdf35c40-ae34-48e0-9cc9-0c9da1808c22