Since we already checked InputStream::KnownSize(), we can assume that
GetSize() returns a valid value, and this check is obsolete.

Replace the bogus GetSize() check and call GetSize() only when
necessary.

Move code from the FAAD decoder plugin.

This loop is completely unnecessary.  We just need to find the first
ADTS frame and feed it into NeAACDecInit().

Eliminate duplicate cleanup code.

Remove the "whence" parameter that is not actually necessary, and only
complicates the InputStream implementations.

Map LogLevel::INFO to G_LOG_LEVEL_INFO, and LogLevel::DEFAULT to
G_LOG_LEVEL_MESSAGE.  Now client connect/disconnect message are only
logged on log_level "secure".

Decouple some more from GLib.

Prepare to migrate away from GLib.  Currently, we're still using GLib
as a backend.

Replaces GLib's GError.

Drop support for the old faacDec* API.

Hide the definition from C code, to prepare the transition to C++.

Pass a callback table to scan_file() and scan_stream(), instead of
returning a tag object.

Add GMutex, GCond attributes which will be used by callers to
conditionally wait on the stream.

Remove the (now-useless) plugin method buffer(), wait on GCond
instead.  Lock the input_stream before each method call.  Do the same
with the playlist plugins.

Make it X_decoder_plugin.c.

This function replaces the replay_gain_info parameter for
decoder_data().  This allows the decoder to announce replay gain
changes, instead of having to pass the same object over and over.