math/openblas: fix build on 12-CURRENT armv6
Note, the build still fails on 11.0-RELEASE armv6:
http://pkg.awarnach.mathstat.dal.ca/data/11armv6-default/2017-02-25_09h14m08s/logs/errors/openblas-0.2.19,1.log
While here also
- Fix portlint warnings
- Add LICENSE_FILE