Add GLSL, HLSL and Cg syntaxes, maybe ARB assembly too

[jansol]

No description provided.

[cmyr]

It's a good Q to consider which syntaxes we should always bundle. Given that we don't have custom syntax support, I think it's reasonable to be pretty liberal, but eventually we might want to trim down the default set to reduce binary size?

[jansol]

I suppose we could ship something like stackoverflow's top 50 languages. It would be nice to have some central place to download additional definitions.