cmd/compile: rename OEFACE to OMAKEFACE and remove OCONVIDATA
The "eface" in OEFACE suggests it's only for empty interfaces, and the
documentation suggests that too. But it's actually used for both empty
and non-empty interfaces, so rename to OMAKEFACE and adjust docs
accordingly.
Also, remove OCONVIDATA. This was used by the 1.18 frontend for
constructing interfaces containing derived types, but the unified
frontend always uses OCONVIFACE instead, so this is unused now.
Change-Id: I6ec5c62f909b26027f2804e5b3373b7a00029246
Reviewed-on: https://go-review.googlesource.com/c/go/+/527336
Auto-Submit: Matthew Dempsky <mdempsky@google.com> Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>