move volatileLoad/Store to new module core.volatile_

[MartinNowak]

No description provided.

[MartinNowak]

requires dlang/dmd#4155

[WalterBright]

Don't care for module names with _ in them. Shouldn't open the door to that.

[dnadlinger]

@WalterBright: The ball has been in your court for almost two months, and now you discover that you don't like this? What else do you propose? Just removing volatile as a keyword now and going straight with core.volatile? Waiting any longer without a decision is not an option.

[JinShil]

Don't care for module names with _ in them. Shouldn't open the door to that.

With volatile reaching end of life soon, this should be temporary: http://dlang.org/deprecate.html#volatile

[WalterBright]

What else do you propose?

I propose my original pull request #892 until volatile becomes available. In the meantime, keyword volatile needs to go through the usual deprecation cycle. I know nobody likes bitop but me, but creating a new temporary file&module named volatile_ sets a bad precedent that we'll be stuck with for years because of backwards compatibility.