Maybe update bp_core_set_uri_globals() for AJAX detection

[DJPaul]

I noticed bp_core_set_uri_globals() has an "Ajax or not?" check. Do we need to update this for 1.6 now that the AJAXURL has changed to admin-ajax.php? I'm not sure what the purpose of this check is.

[boonebgorges]

I think we need this check, because proper path detection is necessary for determining current component, action, etc. Also, I think we need the wp-load.php logic for backward compatibility (themes that still register the old version of ajaxurl). But our primary check should be for WP's DOING_AJAX. See attached patch.

[DJPaul]

Thanks for the patch, Boone. As we'll be testing the ajaxurl change in beta, I think it's safe enough to put this in and test both at the same time.

[djpaul]

(In [6103]) Update bp_core_set_uri_globals() to check for DOING_AJAX when inspecting the request URI.
This is required because of 1.6's change to the javascript ajaxurl variable. The check for wp-load.php remains for backwards compatibility.

Fixes #4263, props boonebgorges