ABI break in libconfig 1.8

Description:

After libconfig updated to version 1.8-1, all ffado applications will fail to start with:

ffado-dbus-server: symbol lookup error: /usr/lib/libffado.so.2: undefined symbol: _ZN9libconfig6Config9writeFileEPKc

Additional info:

• Using libffado 2.4.9-2
• I rebuilt locally using the PKGBUILD against the new version of libconfig and everything seems to work fine

Steps to reproduce:

1. Confirm libconfig v1.8-1
2. Run any libffado application (I used ffado-dbus-server, but it happens with ffado-mixer and others too)