SQL Server 2012 : how to add missing collation
There never has been a "Latin1_General_CP1_CI_AS": it is "Latin1_General_CI_AS" or "Latin1_General_100_CI_AS"

You may be confusing it with "SQL_Latin1_General_CP1_CI_AS" which is legacy, basically.

Saying that, the collation offered at setup varies based on your regional settings. See SQL Server 2005 collation issue during installation for more (I've no idea why US English locale offers a "legacy" SQL collation)

SELECT * FROM ::fn_helpcollations() FH WHERE name LIKE '%Latin%_CI_AS'