riff: K&R formatting cosmetics

Signed-off-by: Diego Biurrun <diego@biurrun.de>
riff: check for eof if chunk size and code are 0

Prevent an infinite loop.

Inspired by a patch from Michael Niedermayer

CC: libav-stable@libav.org

Signed-off-by: Diego Biurrun <diego@biurrun.de>
riff: Move guid structs and helper functions into riff

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Signed-off-by: Diego Biurrun <diego@biurrun.de>
riff: Perform full lookup on WAVEFORMATEXTENSIBLE subformat guid

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Signed-off-by: Diego Biurrun <diego@biurrun.de>
riff: Add ACTRAC3+ guid

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Signed-off-by: Diego Biurrun <diego@biurrun.de>
riff: Factor out WAVEFORMATEX parsing

Makes the code simpler to follow.

Signed-off-by: Diego Biurrun <diego@biurrun.de>