RFR (S) 8024635: Caching MethodType's descriptor string improves lambda linkage performance

[John Rose]

8024635: Caching MethodType's descriptor string improves lambda linkage performance
Summary: Better interpreted and compiled performance of operations in MethodType important to LambdaMetafactory.
Reviewed-by: jrose, twisti, ?
Contributed-by: skuksenko

http://cr.openjdk.java.net/~jrose/8024635/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8024635

Change details:
- Add another one-element cache to MethodType.
- Refactor and simplify the intern table query.
- Refactor slot count logic to remove dead code execution (in interpreter).

Previous Emails:
  http://mail.openjdk.java.net/pipermail/core-libs-dev/2013-September/021370.html

There are enough reviewers for this, but additional review is welcome.

Thanks,
— John