- 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

wordexp(): Avoid leaking the pipe file descriptors to a parallel fork/exec.

This uses the new pipe2() system call added on May 1 (r250159).

wordexp(): Fix syntax validation for backslashes in single-quotes.

wordexp(): Simplify code by deferring work to sh.

wordexp(): Remove wrong IFS usage.

Words in shell script are separated by spaces or tabs independent of the
value of IFS. The value of IFS is only relevant for the result of
substitutions. Therefore, there should be a space between 'wordexp' and the
words to be expanded, not an IFS character.

Paranoia might dictate that the shell ignore IFS from the environment (even
though our sh currently uses it), so do not depend on it in the new test
case.

Eliminate more dead stores.

Found by: Clang static analyzer
MFC after: 7 days

wordexp(3): fix some bugs with signals and long outputs
* retry various system calls on EINTR
* retry the rest after a short read (common if there is more than about 1K
of output)
* block SIGCHLD like system(3) does (note that this does not and cannot
work fully in threaded programs, they will need to be careful with wait
functions)

PR: 90580
MFC after: 1 month

Fix typo: WRDE_DOOFS -> WRDE_DOOFFS.

Noticed by: Stoned Elipot

Terminate execl()'s argument list with a null pointer instead of a
null pointer constant. (The latter may be an integer constant, which
is not correct here.)

Submitted by: Stefan Farfeleder

Use hidden names (_close, _dup2, _waitpid, etc.) where appropriate.

Fix a number of bugs noticed by more extensive testing:
o Call waitpid() if an error occurs after forking the child process
to avoid leaving zombies around.
o Handle the WRDE_DOOFS|WRDE_APPEND combination correctly
o Do not confuse $( substitution with $(( shell arithmetic
(noticed by wollman)
o Handle backslash escaping properly
o Allow $( and ${ to be quoted

Be more consistent with "static".

Add an implementation of the POSIX wordexp() and wordfree() functions,
which perform shell-style word expansion on strings. This is still a
little rough around the edges.

PR: 13420