doc: mention more cygwin 1.7 status

doc: mention more cygwin 1.7 status

* doc/posix-functions/access.texi (access): Mention cygwin 1.5
bug.
* doc/posix-functions/execl.texi (execl): Likewise.
* doc/posix-functions/execle.texi (execle): Likewise.
* doc/posix-functions/execlp.texi (execlp): Likewise.
* doc/posix-functions/execv.texi (execv): Likewise.
* doc/posix-functions/execve.texi (execve): Likewise.
* doc/posix-functions/execvp.texi (execvp): Likewise.
* doc/glibc-functions/canonicalize_file_name.texi
(canonicalize_file_name): Cygwin 1.7 now provides this.
* doc/glibc-functions/euidaccess.texi (euidaccess): Likewise.
* doc/posix-functions/fchmodat.texi (fchmodat): Mention limitation
on AT_SYMLINK_NOFOLLOW.

Signed-off-by: Eric Blake <ebb9@byu.net>