- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

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

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

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