another coverity_branch helper script

that pushes the coverity_branch to origin without switching to it
fixed printf-format: "unsigned long" is "%lu"

Closes CID#75651
merged coverity_branch helper-scripts
make READLINK work on osx

osx provides 'readlink' and 'greadlink', the latter is what we want.
so we
- swap tests (first 'greadlink', fall back to 'readlink')
- check whether the command found supports the '-f' flag