Ask @foonathan how to use libclang + VS on appveyor

[Manu343726]

Aka _fix appveyor build_.

Related: #10, #29

[foonathan]

Here is my Appveyor script: https://github.com/foonathan/standardese/blob/master/appveyor.yml

libclang is preinstalled.

[Manu343726]

I've noticed that you're building clang 3.8 in your Travis script. Clang 3.7 is in the Travis whitelist, and you can take libclang from that package (See https://github.com/GueimUCM/siplasplas/blob/master/.travis.yml#L103). That should reduce your CI builds time.

EDIT: Just install libclang1-${CLANG_VERSION} package.

[foonathan]

I'm not building clang 3.8, I'm downloading it. And given the time it takes Travis to install something, it is faster.

[Manu343726]

And given the time it takes Travis to install something, it is faster.

Good to know.

[foonathan]

Also at the time of setting it up, LLVM's apt mirror was down.

[Manu343726]

Yeah, my builds magically become green some days ago...