select: reject invalid file descriptors

select: reject invalid file descriptors

POSIX requires invalid file descriptors to be detected rather than
silently ignored.  FreeBSD 8.2 detects if fd 0 has been closed
and appears in a set while fd 1 is still open, but mistakenly
optimizes and refuses to check any fds in the set beyond the
maximum open fd.

* m4/select.m4 (gl_FUNC_SELECT): Probe for FreeBSD bug.
* lib/select.c (rpl_select) [!win32]: Work around it.
* modules/select (Depends-on): Add dup2.
* doc/posix-functions/select.texi (select): Document this.