Bug#836599: downgrading severity to normal

[Ghislain Vaillant]

control: severity -1 normal

Previous builds on mips and mipsel have been removed [1]. Downgrading 
the severity of this bug to allow the updated package to transition.

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=836740

Cheers,
Ghis