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

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

Add a new line to top that provides a brief summary of the ZFS ARC memory
usage on hosts using ZFS. The new line displays the total amount of RAM
used by the ARC along with the size of MFU, MRU, anonymous (in flight),
headers, and other (miscellaneous) sub-categories. The line is not
displayed on systems that are not using ZFS.

Reviewed by: avg, fs@
MFC after: 3 days

Add a -P flag to display per-cpu cpu usage stats.

Apply the FreeBSD-local patches.

Obtained from: The ports collection.

This commit was generated by cvs2svn to compensate for changes in r24139,
which included commits to RCS files with non-trunk default branches.

This is the long-awaited import of top into the base system (actually,
the src/contrib/top part right now). This tools is simply too system-
dependant to maintain it in the ports collection.