Utility operators for atomic variables

[LouisJenkinsCS]

I believe that utility operations, such as +, +=, >, >=, <, <=, etc., should be supported for atomic variables. Something like the following should be supported...

var x : atomic int;
var y : atomic int;
x = 1; // x.write(1)
y = x; // y.write(x.read())
x += 1; // x.fetchAdd(1)
assert(x != y); // assert(x.read() != y.read())

Such things are convenient, even if they can be misleading (I.E x += x is not guaranteed to be atomic as they would result in two separate atomic operations) but it should be up to the user.

[bradcray]

@ronawho and I have been talking about making atomics a bit more convenient to work with from time to time as well. I think he has a good handle on what we might want to support (better than I do anyway).