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)

Wohooooo, the method Filter::Reset() has been broken because no
implementation of it has ever been called for a loooong time.
And nobody ever noticed it.  WTF.

Fixes another crash bug caused by commit
64d141f7

Fixes crash bug caused by commit
64d141f7

Caused by commit 64d141f7

This wasn't a serious memory leak, because after a mount failure, MPD
would abort anyway, which is subject to the next commit.

This source file isn't compiled when the database is disabled.

Similar to commit 31ab78ae

Fixes deadlock because FileInputStream::Read() unlocks the mutex
(which was not locked) and then locks it, keeping it locked.  This can
result in a deadlock.  This happens because the archive and the file
mutex are different.

If a directory is a mount point, omit the "directory: " as well.

This bug is years old, but has become more visible now that mount
points are persistent in the state file.

Signed-off-by: FlashSystems <developer@flashsystems.de>

If `SimpleDatabase::Visit` is called on a database that contains a mounted directry the URIs of the elements passed to the callbacks are not prefixed by the mountpoint path. This leads to lsinfo and add not working because they use the wrong URI. This pull request is using the `WalkMount` helper function to create prefixed versions of `VisitDirectory`, `VisitSong` and `VisitPlaylist` to add the correct prefix to the parameters of the callback functions.

This alleviates a problem in which 'volume +1' cannot be undo by
'volume -1' when using alsa hw mixer.

Closes #104