RFR: Caching MethodType's descriptor string improves lambda linkage performance

[Sergey Kuksenko]

Please review the webrev at:

http://cr.openjdk.java.net/~skuksenko/jsr335/8024635/webrev.00/

MethodType.toMethodDescriptorString() is frequently invoked when
generating lambda classes from InnerClassLambdaMetafactory.
Caching resulting string into the field of MethodType  gives +5% - +10%
to lambda linkage performance.

Minor performance improvement: private method "checkPtype" was inlined
and eliminated. "checkRtype" and "checkPtypes" were refactored for
better perfomance in HotSpot interpreter (important for lambda linkage).
overall result +1%.


-- 
Best regards,
Sergey Kuksenko