cmd/5g etc: mechanical cleanup

Run rsc.io/grind rev 796d0f2 on C->Go conversions.

This replaces various awkward := initializations with plain var declarations.

Checked bit-for-bit compatibility with toolstash + buildall.

Change-Id: I601101d8177894adb9b0e3fb55dfe0ed4f544716
Reviewed-on: https://go-review.googlesource.com/6517
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/cmd/internal/gc/init.go b/src/cmd/internal/gc/init.go
index 3c27bd6..5b1dca0 100644
--- a/src/cmd/internal/gc/init.go
+++ b/src/cmd/internal/gc/init.go
@@ -115,7 +115,7 @@
 		return
 	}
 
-	r := (*NodeList)(nil)
+	var r *NodeList
 
 	// (1)
 	namebuf = "initdoneĀ·"