Closes https://github.com/MusicPlayerDaemon/MPD/issues/1168

Fixes -Wformat warnings.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1150

A few exceptions are needed for sources which include COM header
(directly or indirectly).

This fixes lots of shadow warnings, see
https://github.com/MusicPlayerDaemon/MPD/issues/1150

Include the most specific header documented by MSDN instead.

"%lu" is portable - it works with both POSIX and Microsoft flavors.

Fixes a part of https://github.com/MusicPlayerDaemon/MPD/issues/1150

For querying tags, the real song URI should be used, because if the
(display) URI is different, requesting it will not produce a usable
response.  This is a theoretical problem because none of the existing
playlist plugins sets the real_uri.

This requires changing the URI comparison in playlist::TagModified().

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1154

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1156

With the default value CURLAUTH_ANY, libcurl needs to probe for
authentication methods first, and only the second request will have an
Authorization header.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1155

Since we migrated to readthedocs.io, we don't need this target
anymore.  And Meson 0.58.0 apparently has a change breaking this
target.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1161

The clang/libc++ version in xcode10.3 does not support C++17 properly
and cannot build MPD.

The old "ppa:mstipicevic/ninja-build-1-7-2" just provides ninja 1.7
which is too old and breaks the build.

This enables the JACK output plugin on Windows, but doesn't link
against libjack64.dll, instead loads the DLL at runtime with
LoadLibrary().  This kludge avoids the extremely fragile JACK shared
memory protocol by using the system's libjack64.dll, without requiring
the same DLL at build time.

Fixes crash when pausing the default partition after an output was
moved to another partition.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1147

This reverts commit 1532983f.  This
optimization was bad because now all strings match if they are a
prefix of another string, and this caused collisions in the tag string
pool, corrupting the database.

Upcoming release of game-music-emu will support it, details here: https://bitbucket.org/mpyne/game-music-emu/pull-requests/23/rsn-support

The current http output doesn't provide a header for cross-origin support. This prevents to use the mpd http stream directly from an other webapplication due the origin from the webpage differs from then the audio stream.

The fix is to add the following header to the http response:
Access-Control-Allow-Origin: *