add support for unmasked statements

[MkazemAkhgary]

it would be nice to have unmasked statements.

unmasked float x = Foo(); // any expression in this statement should be unmasked

Interestingly, this doesn’t throw an error and compiles fine, but it doesn’t do anything (i.e., still masked).

[pbrubaker]

Would you mind splitting this into two issues please? It's a bug that this compiles, but making this actually work is a feature request. I suggest keeping this the feature request and creating a new one for the bug.

[MkazemAkhgary]

done #2835