llvm 3.5.0 (stable release)

LLVM Polly 3.5.0 requires specific version of Cloog and ISL, rather
than creating separated formulae for these (#508), this commit build
these libraries via resources.
This branch doesn't seem to exist?

```
 git ls-remote http://llvm.org/git/libcxxabi.git
a69d4d917316e4123ec6510845d21ae53b3ecf45	HEAD
a69d4d917316e4123ec6510845d21ae53b3ecf45	refs/heads/master
7e5a90713832cd48cc6e15b9d7a7a94e49ac4f37	refs/heads/release_32
```