RFR: 8170467: (reflect) Optimize SignatureParser's use of StringBuilders

[Claes Redestad]

Hi,

please review this patch provided by Max Kanat-Alexander[1] to improve
performance of sun.reflect.generics.parser.SignatureParser by reducing
number of StringBuilders created and the rate at which they are resized
during typical usage.

Webrev: http://cr.openjdk.java.net/~redestad/8170467/webrev.01/
Bug: https://bugs.openjdk.java.net/browse/JDK-8170467

Thanks!

/Claes

[1] 
http://mail.openjdk.java.net/pipermail/core-libs-dev/2016-November/045046.html