Don't use -dylib-install-name on OS X with GHC > 7.8.

Fixes #1660. Based on a patch by Christiaan Baaij.
Merge pull request #1661 from 23Skidoo/no-dylib-install-name

Don't use -dylib-install-name on OS X with GHC > 7.8.
Add BSD2, close #1649
Add MPL-2.0, close #1654
Allow CC and LD be specified as environment variables when bootstrapping.