This completes the bug fix commit
2065e329; if we clear "queued" then we
must clear "queued_song" as well, or another variant of the assertion
fails.

MPD doesn't use this feature anyway.

This introduces a the new class MakeProject, which is used as a base
class for all Makefile based thirdparty libraries.

On OS X, the "libtoolize" command is some Apple tool. The libtoolize
we want is named "glibtoolize" in Homebrew.

.. and make all library symbols hidden by default.

Saves big amounts of .text section size with --gc-sections, because
only this allows discarding unused functions from those (static)
third-party libraries.

In current Android SDK releases, Ant support was removed. Move the
necessary build steps from the former Ant build system to our Makefile,
and call the required build tools from the Android SDK (aapt and dx),
Java SDK (javac) and Info-ZIP (zip) directly.

[mk: copied from Felix's commit
e52b906dba971a1173f9e8f83d32b52ee9f89af3 in the XCSoar project)

All it does is "sometimes" close the mixer, but that is also done in
the destructor.

Fixes shutdown memory leak.

This is implicitly done by the destructor.

Fixes shutdown memory leak.

The output plugin shall decide whether to insert silence or do nothing
at all.  The ALSA output plugin has already implemented this.
Inserting silence is not necessary or helpful for some plugins, and
may even hurt them (e.g. "recorder").