Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.Approved by: re (implicit)Sponsored by: The FreeBSD Foundation
Match the implementation of the inline function from libkern.h.
Add local ptototype for memset function.
Add trivial MI memset function implementation. GCC mandates theexistence of this function as a linkable symbol in standaloneconfigurations and existing inline memcpy from libkern.h failsthis requirement.