Include lapack dependency, as the new OpenBLAS package no longer bundles LAPACK with itself.
Don't download/install patchelf if it is runnable from $PATH, and install/use it on Travis!
Add USE_SYSTEM_OPENLIBM, enable building of Julia with distribution-provided openlibm
Include openlibm packages in .travis.yml
Merge pull request #2767 from staticfloat/travis

Travis updates