Embed cbc-2.8.6 in to limp-cbc

The main downside to this is that builds (on my MacBook Pro) now take 4-5mins for the limb-cbc package. This will likely make it a bit painful to work on the limb-cbc package itself.

Perhaps we should split out the C++ portion to its own cabal package so that once it is installed then it's quick to iterate on limp-cbc itself.

Having said that, I made it so that you can still use the external Coin/CBC libraries by doing `cabal configure -f-embedded`, so perhaps that would work fine for development of the package itself.