cmd/compile: fix import/export of Init and Def fields.
Change so that the Init and Def fields of assignments and OSELREVC2
nodes are exported/imported properly.
A quirk of iimport.go is that it automatically converts an ODCL node to
an ODCL/OAS sequence (where the OAS is to just zero out the declared
variable). Given that the Inits are properly fixed, o.stmt needs
adjustment for the OSELRECV2 case to skip over the new OAS nodes that
are inserted only on re-import.
Change-Id: Ic38017efca4b7ca9b3952ffbbfca067380902b7a
Reviewed-on: https://go-review.googlesource.com/c/go/+/350809
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Trust: Dan Scales <danscales@google.com>