Fix build with Boost 1.81.0. `<array>` was included by one of those boost headers,
however, it's no longer included as of Boost 1.81.0.

`master` doesn't use `std::array` in this file.

While we're at it, add all necessary inclusion files.

These settings do not work if CURL was compiled with
CURL_DISABLE_PROXY, and cause error "An unknown option was passed in
to libcurl".

Fixes regression by commit 7ab0dfc8

This compile-time option is not about debug logging, but about
curl_easy_strerror().

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1670

Of course, mode=0700 is more secure, but allowing other users access
to new directories is a choice the user should make via umask().  If
the user-chosen umask allows everybody access, MPD should probably
respect that.

This is systemd specific, and Android doesn't have systemd.

The function spl_valid_name() should verify playlist names and prevent
path traversal, but it failed to do so on Windows, because it forgot
to check for backslashes.

This buggy piece of code was already present when stored playlists
were initially implemented in 2006 by commit 08003904, and
even during the many rounds of code refactoring, nobody ever bothered
to verify it.  D'oh!

(Thanks, Paul Arzelier)

snprintf() does not return the (truncated) length actually written,
but the length that would be needed if the buffer were large enough.
This API usage mistake in FormatLastError() can lead to overflow of
the stack buffer, crashing the process (Windows only).

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1676

Fixes spurious linker errors.

If no archive library was found, return from the "plugins" directory
without creating "libarchive_plugins.a".  Empty static libraries are
unsupported on some operating systems such as macOS.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1650

Commit 44ef34db was broken.

Punycode hooray!

It is not explicitly documented whether snd_pcm_name() is allowed to
return NULL:
https://www.alsa-project.org/alsa-doc/alsa-lib/group___p_c_m.html#ga5031edc0422df8db1f70af056a12dd77

But apparently this is legal:
https://github.com/alsa-project/alsa-lib/blob/0222f45d11e8b71bf651b985b00fdb0addbf3eed/src/pcm/pcm.c#L2761-L2762

That's ... surprising!

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1645

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1644

This appears to have been fixed in some recent CURL version.