Was using the wrong parameter.

The former is deprecated by C++14. The standard says they are the same:

The header defines all types and macros the same as the C standard library
header<stdint.h>.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

The former is deprecated with C++14. The standard says both are the same:

The contents and meaning of the header<cstddef>are the same as the C
standard library header<stddef.h>,except that it does not declare the type
wchar_t, that it also declares the type byte and its associated
operations (21.2.5), and as noted in 21.2.3 and 21.2.4.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

The former was deprecated with C++14.

According to the C++11 and C++17 standards, both files are identical.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Fixes
../src/time/ISO8601.cxx:67:24: error: use of undeclared identifier 'strtoul'
        unsigned long value = strtoul(s, &endptr, 10);
                              ^
../src/time/ISO8601.cxx:77:14: error: use of undeclared identifier 'strtoul'
                        minutes = strtoul(s, &endptr, 10);
                                  ^

on NetBSD with clang 9.0.0.

Caused by 2bc127bb

This prepares the migration away from strptime() for Windows
portability.

But the real reason I'm doing this is that strptime() on Apple is
buggy: strptime("14", "%H%M%S") (without separating colons) succeeds
even though only the hour has been parsed.  This fixes recent Travis
failures in the ParseISO8601() unit test.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/685

And allow "Z" suffix after date.

Prepare for adding more flexible parsing.

Move code from Parser.cxx.

This is recommended by the strptime() manpage, because strptime() does
not initialize/set attributes which were not specified in the format
string.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/562

And allow "Z" suffix after date.

Prepare for adding more flexible parsing.

Move code from Parser.cxx.