RFR: JDK-8234896: Tab completion does not work for method references in jshell.

[Jan Lahoda]

Hi,

The tab completion does not propose methods for method references. E.g.:
---
jshell> class C { public static void test() { } }
| created class C

jshell> Runnable r = C::<tab>
---

Produces no proposals. This patch tries to fix that, by proposing 
methods (and the smart code completion will filter methods that have 
acceptable parameter/return types).

Webrev: http://cr.openjdk.java.net/~jlahoda/8234896/webrev.00/
JBS: https://bugs.openjdk.java.net/browse/JDK-8234896

How does this look?

Thanks,
     Jan