xapp_xmag: fix build against Xmu by bumping version

Fix a build issue similar to the one encountered on xapp_listres at
http://autobuild.buildroot.org/results/06d0ef38165769df38047c1f64d4cfae835e9e54/

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Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>