Add an implementation of open_memstream() and open_wmemstream().  These
routines provide write-only stdio FILE objects that store their data in a
dynamically allocated buffer.  They are a string builder interface somewhat
akin to a completely dynamic sbuf.

Reviewed by:	bde, jilles (earlier versions)
MFC after:	1 month
Fix a potential race in returning setting errno when an
association goes down.
Reported by Mozilla in
https://bugzilla.mozilla.org/show_bug.cgi?id=845513

MFC after: 3 days
Fix a typo that prevented booting a kernel that had virtual addresses in
the elf headers.
fix this script so we don't expand the second $FreeBSD since svn thinks
the $ in $1 ends the keyword, and expands it...
mdoc: add missing El.
mdoc: begin sentence on new line.
Remove EOL whitespace.