Improve automatic module handling in module graph construction

Add all automatic modules to roots if at least one automatic module is
added, as per
http://cr.openjdk.java.net/~mr/jigsaw/spec/api/java/lang/module/package-summary.html

compiler/testData/javaModules/unnamedAgainstSeveralAutomatic/main/usage.kt

@@ -0,0 +1,6 @@
+import foo.Foo
+import bar.Bar
+
+fun usage(): String {
+    return "${Foo()}${Bar()}"
+}