The line in cgen.go was lost during the ginscmp CL.
The ggen.go change is not strictly necessary, but
it makes the 5g -S output for x[0] match what it said
before the ginscmp CL.

Change-Id: I5890a9ec1ac69a38509416eda5aea13b8b12b94a
Reviewed-on: https://go-review.googlesource.com/9929Reviewed-by: Russ Cox <rsc@golang.org>