Imported from upstream's 4102d1a503.

Change-Id: I6ddfa8ff88101e330e74958a3ae776f8758eb724
Reviewed-on: https://boringssl-review.googlesource.com/5484
Reviewed-by: Adam Langley <agl@google.com>

Otherwise, in C, it becomes a K&R function declaration which doesn't actually
type-check the number of arguments.

Change-Id: I0731a9fefca46fb1c266bfb1c33d464cf451a22e
Reviewed-on: https://boringssl-review.googlesource.com/1582
Reviewed-by: Adam Langley <agl@google.com>

Initial fork from f2d678e6e8 (1.0.2 beta).

(This change contains substantial changes from the original and
effectively starts a new history.)