Fixed order of cblas and atlas linker flags

They were the wrong way round, causing linking to fail in some cases
Added extern C wrapper to cblas.h include

This ensures that it works with ATLAS's header file, which doesn't include such
a guard itself (whereas the reference version from Ubuntu's libblas-dev does)
Merge pull request #185 from jamt9000/boost-eigen

Fix cblas and atlas linking and cblas include for some linux flavors.