Add svn:keywords property to Makefile.

Approved by:	re (gjb)
Correct the svn:keywords value.

Approved by:	re (gjb, implicit)
Fix module build when device ata is not in kernel config.

Sponsored by:	The FreeBSD Foundation
Build-tested by:	gjb
Approved by:	re (delphij)
If the last page of the file is partially full and whole valid
portion is invalidated, invalidate the whole page.  Otherwise,
partially valid page appears on a page queue, which is wrong.  This
could only happen for the last page, because only then buffer which
triggered invalidation could not cover the whole page.

Reported and tested by:	pho (previous version)
Reviewed by:	alc
Sponsored by:	The FreeBSD Foundation
Approved by:	re (delphij)
MFC after:	2 weeks