crypto/elliptic: tolerate large inputs to IsOnCurve methods
The behavior of all Curve methods and package functions when provided an
off-curve point is undefined, except for IsOnCurve which should really
always return false, not panic.
Change-Id: I52f65df25c5af0314fef2c63d0778db72c0f1313
Reviewed-on: https://go-review.googlesource.com/c/go/+/361402
Trust: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Filippo Valsorda <filippo@golang.org> Reviewed-by: Roland Shoemaker <roland@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>