This trivially adds a name for marshalOptions and unmarshalOptions
instead of always having it be underscore.
This assists the use of patches that rely on this variable.
Change-Id: I4c23901c93f0362aff412339912522f92749d659
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/263627
Trust: Joe Tsai <joetsai@digital-static.net>
Reviewed-by: Damien Neil <dneil@google.com>