The equal methods were only there for testing, and I remember regularly
getting them wrong while developing tls-tris. Replace them with simple
reflect.DeepEqual calls.

The only special thing that equal() would do is ignore the difference
between a nil and a zero-length slice. Fixed the Generate methods so
that they create the same value that unmarshal will decode. The
difference is not important: it wasn't tested, all checks are
"len(slice) > 0", and all cases in which presence matters are
accompanied by a boolean.

Change-Id: Iaabf56ea17c2406b5107c808c32f6c85b611aaa8
Reviewed-on: https://go-review.googlesource.com/c/144114
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>