Apparently C does not promise this, only that casting zero to a pointer
gives NULL. No compiler will be insane enough to violate this, but it's
an easy assumption to document.

Change-Id: Ie255d42af655a4be07bcaf48ca90584a85c6aefd
Reviewed-on: https://boringssl-review.googlesource.com/18584
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>

Whether UCHAR_MAX expands to a signed or unsigned number appears to be a
matter of some debate. Or the Android headers are wrong. Just add a cast
and not think about it too hard.

Change-Id: I84e928bdfe459a9129cde276c82b60a318533552
Reviewed-on: https://boringssl-review.googlesource.com/15385
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>

C leaves some details as implementation-defined. We only support
implementations which define things consistent with the obvious
representation on current machines.

Change-Id: I255a2e54a86c8a7d987dea51ea7168ad66ad9ddd
Reviewed-on: https://boringssl-review.googlesource.com/15305
Reviewed-by: Adam Langley <agl@google.com>