Version 2.5 fixed an API oddity, however it broke API compatibility,
at least with C++.  Disable the workaround when a libavformat version
is detected that is recent enough.

The "::" to explicitly refer to the global namespace appeared like a
good idea in C++, but it breaks with C libraries that implement
standard functions using macros (e.g. musl).

There are code paths (mostly error cases) in which it is possible to
initialize an AudioOutput and then kill it without ever calling
audio_output_new().  In such a case, its destructor will attempt to
free a mixer that was never initialized, leading to an attempt to
take out a lock on a mutex that was similarly never initialized,
which hangs forever.

Fix by always initializing the mixer appropriately.

Due to security vulnerabilities.

Avoids crash because Close() invokes a call on a destructed
NfsConnection.

Avoid calling NfsConnection::RemoveLease(), because the lease has been
removed already.

Clean up the "state" to indicate that there is no longer any
asynchronous operation.  Fixes another NFS-related crash due to
cleanup of a non-existing asynchronous operation.

Avoids a crash that occurs when NfsConnection::OnSocketReady()
dereferences itself before returning.

During the NfsLease::OnNfsConnectionFailed() call, the old (defunct)
nfs_context may be used to close file handles.  Such code does not yet
exist, but will be added soon to fix other bugs.

Fixes potential second mount attempt after the old connection to the
NFS server was shut down.

libmp4v2 is licensed under MPL 1.1, which is incompatible with GPLv2.
Unfortunately, this means that we must remove the plugin.

More information can be found in the Debian bug report:

 http://bugs.debian.org/767504

Set the Error when zzip_seek()==-1 and not on success.  Fixes a crash
after seeking.

Android releases were missing since 0.19.1.

A negative uid value means it's not a "local socket" (PF_LOCAL).
uid==0 means user "root" connected.

Must return -1 on error, not 0.  0 is root.