Hand-audit compiler warning results which we wouldn't want to have on-by-default.

These warnings aren't definitely indicative of bugs in our code, and don't seem to be possible for us to fix in all cases. Still, it might be worth auditing all the cases where these warnings trigger, since they might indicate bugs or possible areas of improvement.

  strict-overflow=3...5 (4.2)

    Behaves pretty differently on different GCC versions.

    We get warnings for just about every case where we have pointer
    math in an addition. That seems nutty.

  padded (3)
    Not a mistake.  Worth looking over for hand-audit purposes, but mostly
    harmless.

  unsafe-loop-optimizations (4.1)
    Worth hand-auditing, but triggers on every kind of interesting for loop.

  covered-switch-default
    Usually this is defensive programming, but it could be a mistake
    in some cases, or could cover up future mistakes?