distcheck: Include the .version file in the package

Fixes on Ubuntu

make[1]: Entering directory '/home/builder/jenkins/workspace/libosmo-abis/label/linux_amd64_ubuntu_1504/libosmo-abis-0.3.2.5-7c93/_build/sub'
echo 0.3.2.5-7c93 > ../../.version-t && mv ../../.version-t ../../.version
/bin/bash: ../../.version-t: Permission denied
Makefile:891: recipe for target '../../.version' failed
make[1]: *** [../../.version] Error 1
1 file changed