Correctly locate Clang [Fixes 250]

[shahid-pk]

Proposed for #250 and #243 Clang locating issues.

[janvorli]

The clang naming is not a general Linux problem. It is interesting that e.g. in my Ubuntu, all the llvm-xxx commands have the 3.5 suffix, but the clang doesn't.

[shahid-pk]

so what would you suggest we do here ? check for both clang and clang-* for linux?.
clang is also clang-* , actually their are two versions of clang available on ubuntu clang 3.4 and clang 3.5, if you install clang 3.4 , you get clang and clang++ commands but if you download clang-3.5 you get clang-3.5 and clang++-3.5 . I have checked it but i may be wrong.

[janvorli]

Yes, it seems like we need to do it that way.

[shahid-pk]

ok

[shahid-pk]

@janvorli comments addressed .

[shahid-pk]

extra commit squashed

[janvorli]

LGTM, thanks for fixing it.

[mmitche]

LGTM