Core: add params to functions in the multisite abstraction file.

WordPress Multisite has several functions that aren't present when WordPress is run in single site mode.
To simplify our compatibility with these configurations, BP uses `bp-core-wpabstraction.php` to declare wrapper versions of the relevant function.

Prior to this commit, we had several of these functions that didn't have the same parameter declarations as the real functions.
This has not caused any compatibility issues with PHP (parameters can be passed to a function that doesn't explicitly require arguments, without error), but is caught by some PHP static analysers, such as scrutinizer-ci.com.

See https://scrutinizer-ci.com/g/buddypress/BuddyPress/inspections/5e580ae2-ae16-4cbc-b191-95b0ce72b112/issues/files/src/bp-blogs/bp-blogs-functions.php?status=new&orderField=path&order=asc for an example report of this.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@9288 cdf35c40-ae34-48e0-9cc9-0c9da1808c22