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GetSize() returns a valid value, and this check is obsolete.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.

Variable-length arrays are not allowed in C++.

If the offset is out of range, the seek will simply fail.  Not a
problem.

The plugin assumes that the size is known, but does not verify it at
runtime.

Eliminate duplicate definition (in input plugin and decoder plugin).

When no track is found the error is now properly set.
Previously the calling function tried to log an undefined
error, which resulted in a crash. MPD falls back to
ffmpeg for unsupported tracks, such as ALAC.

This should fix issue 4051.

This plugin uses the MP4v2 library to play mp4/m4a files.
It is limited to file_decode.

They are only used inside dsdiff_read_metadata_extra().

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.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>

Reduce duplicate code.

(see https://www.xiph.org/vorbis/doc/v-comment.html for Details)

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