[!HAVE_CONFIG_H] (xstrtoul, error, close_stdout): Added stubs

[!HAVE_CONFIG_H] (xstrtoul, error, close_stdout): Added stubs
to allow standalone compilation.

(wipefile): Added support for emulating /dev/fd/# files even if
the OS doesn't support them.  From Paul Eggert.

(main, usage): Changed --device short option to -D.

(wipefd, do_wipefd): Renamed function to do_wipefd and added
separate wipefd that performs sanity checks on externally-opened file
descriptors, such as not append-only.  From Paul Eggert.

(do_wipefd, isaac_seedfd): Do not read file for any reason.
if the file is low-entropy, it's a security hole.
(wipefile) Changed to open O_WRONLY and chmod to write-only when
forcing.
(isaac_seedfd) Function deleted as unnecessary.
From Paul Eggert.

(dopass): Dynamically fall back to fsync() if fdatasync() fails,
since POSIX, in their infinitesimal wisdom, encourage implementations
that return constant -1, making compile-time testing useless.
From Paul Eggert.

(dopass): Changed to support a size of -1 to mean "unknown".
This entailed changing to a counting-up offset rather than couting-down
cursize for the central state variable.  Also changed size argument to
be call-by-reference so that it can be passed back once known.
(sizer) Function deleted as unnecessary.
(wipefd): Changed to match.  From Paul Eggert

(dopass): Try to skip over bad blocks in destination files.
Also added ftruncate() for more complete destruction of metadata.

(main, usage): Changed "-" to stand for standard output.
(wipefd): Added error message to detect conflict with -v.

(dopass): Added periodic fsync() calls to keep the pass progress
display in sync with reality.  Hopefully they're sufficiently far spaced
that throughput isn't affected.  It might be a good thing to do even in
non-verbose mode, to avoid filling up the kernel caches with dirty data.
Also added ftruncate() for more complete destruction of metadata.

(quotearg_colon): New function to print
pathological filenames properly.
[!HAVE_CONFIG_H] (quotearg_colon_buf) New internal helper function
that does most of the work.
(wipefd, do_wipefd, dopass) Now take a qname (pre-quoted name) argument.
(wipename, wipefile, main) Changed diagnostics to use quotearg_colon.
Error messages are also in a more uniform format.
From Paul Eggert.

(struct Options, main, do_wipefd): Added -s/--size=N flag.
(xstrtoul): Added support for valid_suffixes to help this.
(usage) Documented it.

(error): Changed some arguments from N_() to _(), since error()
does not translate its argument.  I think this is a bug.

(struct Options do_wipefd, wipefd, wipefile, main): moved passes
argument into the Options structure as n_iterations, which is now a
size_t.  From Paul Eggert.

(isaac_seed_start, isaac_seed_data, isaac_seed_finish): New functions
to manage seeding of RNG with arbitrary-sized data.
(isaac_init): commented out as dead code.
(isaac_seed): changed to use new functions to prevent any possibility of
a buffer overflow.

(isaac_seed): Added support for Solaris' gethrtime()
configure.in: Corresponding feature test.  From Paul Eggert.

(wipename): Change remove() to unlink() for speed & portability.
Use lstat() instead of access() to see if a filename is taken.  This
works even on dangling symlinks and avoids the suid problems of
access(2).  From Paul Eggert.

(isaac_seed_machdep): New function for reading cycle counters