Prepare the transition to std::mutex.

This enables the input buffer for remote files and caches file
contents in MPD.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/376

Let the caller decide what to do with the original exception.

Preserve the original exception.

using the device "default" brings this plugin into line with the AlsaOutputPlugin; and a sample rate of 48kHz is more widely used as a native default for modern hardware than 44.1kHz

Also fixes an inconsistency between the docs and code.

input/plugins/AlsaInputPlugin: introduce mpd.conf config block to allow user to override the builtin defaults

input/plugins/AlsaInputPlugin: extend the alsa uri parsing to permit specification of the desired pcm audio format in the uri

libcdio_paranoia was split from libcdio in version 90, and at the same
time, the header was moved from cdio/paranoia.h to
cdio/paranoia/paranoia.h.  We can easily detect this version at
compile time which is faster than configure time.

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.

This call was missing, causing very high CPU usage when the ALSA
output plugin was used with dmix.

Closes #391

The `bool` return value isn't used anymore, so we can just return the
parsed object instead of passing it as an output parameter.

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.

Required according to RFC 3986:

> An implementation should accept uppercase letters as equivalent to
> lowercase in scheme names

Closes #330