Implement hash-checking on downloaded dependencies

Dependencies will be checked at extraction-time, and have their checksums stored
in deps/checksums The deps/jlchecksum command tests a given filename against the
checksums stored in that file, supporting MD5 and SHA512 checksums for all
recorded files.  SHA512 is preferred, with MD5 available as a fallback in the
case that `shasum` is not available.  If the hashes do not match, an error is
thrown and compilation is halted.  If a file is asked for and no hash has been
stored for that file, a warning is printed but compilation continues
Add in openblas-v0.2.9.rc1 for Windows downloads