Remove no-longer-necessary trademark notices.

(Thanks to Arthur David Olson.)
* private.h, zic.c: Remove UNIX notices.
Check POSIX file name restrictions more carefully.

Also, document the longstanding exceptions to POSIX.
Derived from Arthur David Olson's patch in:
http://mm.icann.org/pipermail/tz/2014-June/021052.html
* Theory: Document the exceptional file name components in 'etcetera'
and 'backward' that contain '+' or digits, or are too long.
* zic.8 (DESCRIPTION): Document the change to zic.
* zic.c (component_length_check, namecheck): New functions.
(dolink, writezone): Use them to check that file name components
obey the POSIX rules, and do not contain "." or "..".
* NEWS: Document the above.
Add 'Thanks' for previous change.
Go back to ASCII in *.txt files, too.

For *.txt files, UTF-8 is not that important, and avoiding it
is better for users with older or misconfigured manpage readers.
* Makefile (check_character_set): Check that *.txt files
contain only safe characters.
($(MANTXTS)): Build *.txt files in the C locale, not in en_US.utf8.
'zic -v' now warns about all '.'s in output file names.

* zic.c (componentcheck, namecheck): Warn about all '.'s in
the file name, not merely about "." and ".." file name components.
* zic.8 (DESCRIPTION), NEWS: Document this.
* Theory, NEWS: Also document EST5EDT etc. as exceptions.

Use the term "legacy names" for exceptions.
A few more spelling, accent, and commentary cleanups.
* zic.8, NEWS: Document character encoding issues better.

(Thanks to Guy Harris for reporting the problem.)
Avoid <ctype.h> locale problems.

* zdump.c, zic.c: Don't include <ctype.h>, because the behavior if
its macros is locale-dependent if HAVE_GETTEXT, and we want the C
locale's semantics.  Instead, use portable replacements for
ctype.h operations, with the desired semantics.  All uses of
isalpha etc. replaced by calls to new functions is_alpha etc.  or
by inline code.
(isascii): Remove.
(is_alpha): New function.
* zic.c (doabbr): Simplify by using is_alpha.
(is_space): New function.
* NEWS: Document the above.
* private.h, zdump.c (TZ_DOMAIN): Look at HAVE_GETTEXT,

not TZ_DOMAINDIR, when deciding whether to define.  This fixes a
recently-introduced typo.  Found by compiling with -DHAVE_GETTEXT
under GNU/Linux.
Fix some 'zic' issues when run as root.

* zic.c: Use angle brackets for <sys/stat.h>.
(dolink): Don't try to link from a directory, as this can
cause trouble on some systems when superuser.
(dolink, itsdir): Rewrite to avoid use of 'access', which is
problematic when setuid.
(itsdir): If S_ISDIR is defined, use plain 'stat' and S_ISDIR;
that's more reliable.  Return -1 if trouble; all callers changed.
(mkdirs): Simplify by using mkdir-itsdir rather than
itsdir-mkdir-itsdir.  Don't assume strerror preserves errno.
'zic' now rejects output file names with '.' or '..' components.

* zic.8, NEWS: Say that "." and ".." file name
components are not allowed in output file names.
* zic.c (componentcheck, namecheck): Do not allow such
file name components.
Mention more JavaScript libraries.

* tz-link.htm, NEWS: Mention Moment Timezone, TimezoneJS.Date, Walltime-js,
and Timezone.  (Thanks to a heads-up from Matt Johnson.)  Also, list
license for timezone-olson.
* zic.8: Fix formatting of long URL.

* zic.8: Format the URL better, by using groff's .URL macro,
falling back on a portable alternative for non-groff implementations.
* leap-seconds.list: Copy from current NIST version.
More spelling and accent fixes.

Plus, update a now-obsolete source for Samoa's late-2011 change to the
International Date Line.
* asctime.c, newctime.3, newtzset.3: Don't imply ASCII is required.
Fix glitches with '-' and italics in man pages.

Using '\-' to denote ASCII minus has problems in groff output, since
it generates a minus sign in the current font, and if you cut and
paste from the documentation the resulting text won't work.  To avoid
the problem, define a string \*- that expands to ASCII minus in a
constant-width font in groff.  Also, change some instances of \(mi and
\(pl to use plain \- and +, since we no longer need special fonts for
these.  Finally, remove some no-longer-needed instances of "\^" after
italicized words.
Use AEST/AEDT etc. instead of EST etc. for Australian abbreviations.

* NEWS, australasia (Aus, Australia/Darwin, AW, Australia/Perth)
(Australia/Eucla, AQ, Holiday, Australia/Brisbane, Australia/Lindeman)
(AS, Australia/Adelaide, AT, Australia/Hobart, Australia/Currie, AV)
(Australia/Melbourne, AN, Australia/Sydney, Australia/Broken_Hill)
(LH, Australia/Lord_Howe, Antarctica/Macquarie):
Prefix Australian time zone abbreviations with "A", and switch
from "ST" to "DT" to denote daylight saving time.  (Thanks to Ian
Abbott, Russ Allbery, Timothy Arceri, Alan Barrett, Stuart Bishop,
Shaun Bouckaert, Stephen Colebourne, Tobias Conradi, Mark Davis,
Robert Elz, Clive D.W. Feather, Dennis Ferguson, Edwin Groothuis,
Guy Harris, John Hawkinson, John Haxby, Brian Inglis, Paul Koning,
Kevin Lyda, Curtis Manwaring, Alan Mintz, Arthur David Olson, Matt
Paine, David Patte, Tim Parenti, random832, Derick Rethans, SM,
Peter Stagg, Rich Tibbett, Bennett Todd, and Garrett Wollman for
their contributions to this topic.)
A few more fixes related to AEST/AEDT etc.  (Thanks to Tim Parenti.)

* Theory: Use CST instead of EST in the example, so that it matches
the current database.
* antarctica (Antarctica/Casey): AWST, not WST.
* asia (Asia/Jayapura): ACST, not CST.
* australasia: Prepend "[A]" to "EST" in quote about EST.