Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

WARNS=2 is going to be the default, so don't specify it. Use __FBSDID().

Fix some trivial warnings and clamp down with WARNS=2

MFC after: 1 week

This commit was generated by cvs2svn to compensate for changes in r1590,
which included commits to RCS files with non-trunk default branches.

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