RFR 8134279: jjs should support multiple line input to complete incomplete code

[Sundararajan Athijegannathan]

Please review http://cr.openjdk.java.net/~sundar/8134279/ for 
https://bugs.openjdk.java.net/browse/JDK-8134279

PS. In addition to the enhancement, I'm fixing this line ->
+        new LinkedHashMap<String, List<String>>(32, 0.75f, true) {

in PackagesHelper to make sure the code compiles with jdk9 as well as jdk8u.

Thanks,
-Sundar