runtime: shift the index for the sort by one.

Makes the code look cleaner, even if it's a little harder to figure
out from the sort invariants.

R=rsc
CC=golang-dev
https://golang.org/cl/165061

src/pkg/runtime/chan.c

@@ -660,12 +660,8 @@ runtime·selectgo(Select *sel)
 	// sort the cases by Hchan address to get the locking order.
 	for(i=1; i<sel->ncase; i++) {
 		cas = sel->scase[i];
-		for(j=i-1; j<i && sel->scase[j]->chan >= cas->chan; j--)
-			sel->scase[j+1] = sel->scase[j];
-		// careful: j might be (unsigned)-1
-		// 6c trips on sel->scase[j+1] in that case by rewriting it to
-		// sel->scase[j] + 8.
-		j++;
+		for(j=i; j>0 && sel->scase[j-1]->chan >= cas->chan; j--)
+			sel->scase[j] = sel->scase[j-1];
 		sel->scase[j] = cas;
 	}