Configure travis to perform a 32-bit build

Besides that, `before_install`/`after_success` code was moved to travis.sh since
it provides greater flexibility with the build matrix(we get small speed
improvements by installing only what's necessary for the environment). Now the
clint.sh script is only ran in the unittest build which is the fastest one(so we
offload more work to it)
Fix clint.sh wrapper script

It wasn't exiting when one of the clint checks failed