Travis CI: trying to avoid stalling builds (#627).
Travis CI: trying to avoid stalling builds (#627).

To use ninja still resulted in a stalling build on Linux while it
simply crashed g++ on OS X. So, now trying to make -j 3...

mirams/opencor,Fairly/opencor,Fairly/opencor,mirams/opencor,Fairly/opencor,mirams/opencor,Fairly/opencor,Fairly/opencor,mirams/opencor,mirams/opencor