cmd/5g etc: merge simple case expressions onto fewer lines

The c2go translation left a lot of case expressions on separate lines.
Merge expressions onto single lines subject to these constraints:

* Max 4 clauses, all literals or names
* Don't move expressions with comments

The change was created by running http://play.golang.org/p/yHajs72h-g:

$ mergecase cmd/internal/{ld,gc,obj}/*.go cmd/internal/obj/*/*.go

Passes toolstash -cmp.

Change-Id: Iba41b390d302e5486e5dc6ba7599a92270676556
Reviewed-on: https://go-review.googlesource.com/7593
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
diff --git a/src/cmd/internal/gc/init.go b/src/cmd/internal/gc/init.go
index 8aaed8c..b3a6a00 100644
--- a/src/cmd/internal/gc/init.go
+++ b/src/cmd/internal/gc/init.go
@@ -54,10 +54,7 @@
 	// are there any interesting init statements
 	for l := n; l != nil; l = l.Next {
 		switch l.N.Op {
-		case ODCLFUNC,
-			ODCLCONST,
-			ODCLTYPE,
-			OEMPTY:
+		case ODCLFUNC, ODCLCONST, ODCLTYPE, OEMPTY:
 			break
 
 		case OAS: