Groups: fix singular string translation in wp-admin members list pagination

See #5767

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8780 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Improve pagination label strings for all components

“Viewing 1 site” reads better than “Viewing site 1 to 1 (of 1 site)”,
regardless of the language you’re using.

Fixes #5767

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8781 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Legacy forums: correctly use an integer for `_n` calls when building the pagination labels

Previously, the number used was the (string) return value from
`bp_core_number_format`. That function uses `number_format_i8n`
internally, which can return values such as “1,000” — which would cause
`_n` to pick the wrong singular/plural string at runtime.

See #5767

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8782 cdf35c40-ae34-48e0-9cc9-0c9da1808c22