fix ghc 7.6.1
Merge branch 'virtualbox-guest-bump-to-4.2.6' into develop

* virtualbox-guest-bump-to-4.2.6:
  Upgrade VirtualBox Guest Additions to 4.2.6
Merge branch 'fix-ghc-gmp-misconfiguration' into develop

* fix-ghc-gmp-misconfiguration:
  fix ghc 7.6.1