New keyword 'threadlocal' as a substitute for `static` on global variables

[Kyle Rocha]

This is a minor one, but I always have to do a double take on static globals. It's semantically different than a static global in c/c++.

I think a new keyword like threadlocal may be more appropriate to clarifying how the variable is used. Seems like it would also pair better with groupshared as well.

[Mateusz Kielan]

+1