MFS9 r254966:
Add missing mergeinfo from head for stabe/9 revisions: 252995 253168 253169

Reviewed by:	gjb
Approved by:	re (gjb)
MFS9 r254953, itself an MFC of r254942 and r254952:
Make alternate layout ``opt-in'' and add support for named releases.
Minor edit to version.4th(8) manual and stack-leak fixes while here.

Approved by:	re (gjb)
Merge branch 'releng/9.2' of https://github.com/freebsd/freebsd into releng/9.2