This is similar to https://github.com/MusicPlayerDaemon/MPD/commit/b177bffa6a5f1b69639b6cd759dcb16fdd76e5e2, in that it fixes the Windows issue of connecting to the open socket. Also, the listen_socket is set to AcceptNonBlock after the connection anyways.

Since we switched from autotools to Meson in commit
94592c14, we don't need to include
`config.h` early to properly enable large file support.  Meson passes
the required macros on the compiler command line instead of defining
them in `config.h`.

This means we can include `config.h` at any time, whenever we want to
check its macros, and there are no ordering constraints.

`__linux` is the deprecated non-standard macros which appears to be
not present at all on PowerPC.

Closes #398

So long, autotools!  This is my last MPD related project to migrate
away from it.  It has its strengths, but also very obvious weaknesses
and weirdnesses.  Today, many of its quirks are not needed anymore,
and are cumbersome and slow.  Now welcome our new Meson overlords!

The number of MPD installs on Android < 5.0 is negligible, and that
API version introduces lots of useful features for MPD.

Fixes the NFS client build, closes #305.

Only _WIN32 is defined by the compiler, and WIN32 is not standardized
and may be missing.

Closes #169

Apparently, connecting a socket to a loopback address can block on
Windows, and a non-blocking socket will return WSAEINPROGRESS.  This
broken PoorSocketPair() in commit 2119e4fd, which made the socket
non-blocking right from the start.  This fix postpones the
ioctlsocket(FIONBIO) call until after the connect().

Closes #134