Quiet align.chpl errors on Intel and PGI.

Changed align.chpl to better demonstrate the original intent.
Added a new future to demonstrate the compiler-dependent behavior.

I agree that a future like this should be filed to track the issue (and wouldn't be surprised if other similar ones already existed -- I think you've filed some like this before -- ideally, the headings should be unified if you can find any of them).  But I disagree with the proposal that Chapel should have to implement integer overflow consistently across all platforms, at least, not when --fast is thrown (which would suggest that it should be a property of the implementation, not the language).  The reason being that we'll never be competitive performance-wise if every integer addition has to have a runtime check for it (and because people are used to performance-oriented languages having this undefined overflow property because their processors do).

We've discussed several times before having an on-by-default/off-when-fast mode that checks for wraparound at runtime and throws a warning/error at runtime when it does occur (or an exception as you propose just below).  Either because the result is poorly defined (signed ints) or because it can be a source of unexpected bugs and surprises in user code (unsigned ints).  I strongly prefer this approach over making integer wraparound well-defined.

There's no need to change anything here just because I disagree (futures can state opinions after all), but you could also capture my perspective in the .future for future readers to save me the trouble of restating the argument later.