Split llvm repository

[amigalemming]

I propose to split the repository such that there is one repository per Cabal package. This allows to set git tags synchronously to Cabal package versions and allows according branching. Another reason is that there are many forks of the high-level llvm interface and I cannot see, why one package should be coupled with llvm-base.
For this reason I also propose to rename llvm to llvm-fd, since it uses functional dependencies, where my forked package named llvm-tf uses type families. But maybe the rename should be in a separate ticket.