The sample plugin/extension msvc10 project files and Makefiles have recently been updated in
mmsource-central and
sourcemod-central, including the addition of configurations for building for CS:GO.
Also check out the
MM:S Dev Wiki to see the
Porting to Swarm and CS:GO article, and additionally the
Porting to Left 4 Dead article first if you're coming up from CS:S or an earlier engine.
The CS:GO sdk can be found
here.
Anything outside of the public/ dir, aside from cusercmd and ctakedamageinfo are unlikely to have been reversed, but it should be plenty for plugins. Feel free to request more.