RFR: 8196331: Optimize Character.digit for latin1 input

[Claes Redestad]

Hi,

for the latin1 block of CharacterData we can improve the
digit(int, int) implementation by providing an optimized lookup
table. This improves microbenchmarks exercising Integer.parseInt,
Long.parseLong and UUID.fromString etc by around 50%for typical
inputs.

Webrev: http://cr.openjdk.java.net/~redestad/8196331/open.00/
Bug: https://bugs.openjdk.java.net/browse/JDK-8196331

The lookup array is pre-calculated to minimize startup impact
(adds 1,027 bytecodes executed during initialization)

/Claes