libsndfile: security bump to version 1.0.26

Fixes:
CVE-2014-9496 - SD2 buffer read overflow.
CVE-2014-9756 - file_io.c divide by zero.
CVE-2015-7805 - AIIF heap write overflow.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>