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

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

Use aux vector to get values for SSP canary, pagesize, pagesizes array,
number of host CPUs and osreldate.

This eliminates the last sysctl(2) calls from the dynamically linked image
startup.

No objections from: kan
Tested by: marius (sparc64)
MFC after: 1 month

Add getpagesizes(3). This functions either the number of supported page
sizes or some number of the sizes themselves. It is functionally
compatible with a function by the same name under Solaris.

Reviewed by: jhb