Don't warn about valid time zone abbreviations. POSIX through 2000
says that an abbreviation cannot start with ':', and cannot contain
',', '-', '+', NUL, or a digit. POSIX from 2001 on changes this
rule to say that an abbreviation can contain only '-', '+', and
alphanumeric characters from the portable character set in the
current locale. To be portable to both sets of rules, an abbreviation
must therefore use only ASCII letters." Adapted from tzcode2015f.
OK deraadt@ mestre@

zdump(8) needs to read files so it needs pledge(2) rpath promise

After discussion with tb@, deraadt@ and millert@, this was also OK'ed by them

exit() after perror() for pledge failure. Perhaps this got introduced
as a test idiom, either when pledge was young or during the transition
to strings.... dunno

pledge() "stdio" includes trusting open&read of the root-owned timezone
databases located at system paths (a reasonable bar had to be chosen; in
the future we can replace the interfaces, since this effort is identifying
them and placing their paths in a visble place), so this program only
needs "stdio"
ok doug

KNF and other style adjustments to make this more scrutible.
reviewed by millert

pounce on a reallocarray opportunity before tedu

exit() cleanup. don't have to call it in a loop.
usage() always takes the same stream and status arguments (despite a
comment indicating perhaps it shouldn't), so make it void

remove support for floating or unsigned time_t. leave the incorrect comment
** time_t is signed. Assume overflow wraps around.
as a warning for future generations.

uncast

remove INITIALIZE macro and do it the hard way.

unifdef have gettext. don't have it, won't have it.

deregister

sort | uniq includes, and use <> instead of quotes

move zic and zdump source to appropriate directories