update calls to Split for API change: 0 no longer means unbounded

R=rsc
http://codereview.appspot.com/1748044
diff --git a/compiler/generator/generator.go b/compiler/generator/generator.go
index 5e103d2..176c94f 100644
--- a/compiler/generator/generator.go
+++ b/compiler/generator/generator.go
@@ -292,7 +292,7 @@
 // It then sets file name mappings defined by those entries.
 func (g *Generator) CommandLineParameters(parameter string) {
 	g.Param = make(map[string]string)
-	for _, p := range strings.Split(parameter, ",", 0) {
+	for _, p := range strings.Split(parameter, ",", -1) {
 		if i := strings.Index(p, "="); i < 0 {
 			g.Param[p] = ""
 		} else {