cmd/compile/internal/types2: review of conversions.go
The changes between (equivalent, and reviewed) go/types/conversions.go
and conversions.go can be seen by comparing patchset 1 and 2. The actual
change is just removing the "// UNREVIEWED" marker.
Change-Id: I86d20d8100ec29fe3be996b975c9b4aff01be85e
Reviewed-on: https://go-review.googlesource.com/c/go/+/294509
Trust: Robert Griesemer <gri@golang.org> Reviewed-by: Robert Findley <rfindley@google.com>