Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.Approved by: re (implicit)Sponsored by: The FreeBSD Foundation
Import the preliminary port of the TTM.The early commit is done to facilitate the off-tree work on theporting of the Radeon driver.Sponsored by: The FreeBSD FoundationDebugged and tested by: dumbbellMFC after: 1 month