Remove GSourceFunc casts

Convert the callback into a real GSourceFunc.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
2 jobs for !14 with GSourceFunc in 1 minute and 19 seconds (queued for 2 seconds)
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Status Job ID Name Coverage
  Build
passed #9807
build

00:00:31

 
  Distcheck
passed #9808
distcheck

00:00:47