LLVM 7.0.0 Release

It's good to be coming back to the llvm-dev list... from the time of
LLVM 3.x releases :).

We have added these as Collective Knowledge packages, and tested on
both armv7a (Odroid XU3) and aarch64 (Linaro HiKey960).

You can check them (on Linux, Windows and MacOS; with x86 or arm) as follows:

$ sudo python -m pip install ck
$ ck pull repo:ck-env
$ ck pull repo:ctuning-programs

$ ck install package:compiler-llvm-6.0.1-universal
$ ck install package:compiler-llvm-7.0.0-universal

$ ck virtual env --tags=compiler,llvm
$ ck compile program:cbench-automotive-susan
$ ck run program:cbench-automotive-susan