Iterate on theme compatibility content replacement order. Introduce bp_do_theme_compat() and other helper functions to avoid breaking on nested calls to the_content() or nested usages of 'the_content' filter.

Also, experiment with not adding/removing all_filters from 'the_content' for a bit, and see if any issues come up in testing with other plugins active.

See #5021.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7131 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Improvements to bp_theme_compat_reset_post() to use WP_Post class. See #5021.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7132 cdf35c40-ae34-48e0-9cc9-0c9da1808c22