RFR: 8015522 - CharSequence.codePoints can be faster

[Henry Jen]

Hi,

Please review
http://cr.openjdk.java.net/~henryjen/tl/8015522.0/webrev/

This webrev is based on previous suggestion from Martin Buchholz while
keep the lazy-binding nature without seize the length at construction time.

The benchmark shows ~50% performance increase, mainly from reduce of
operation, for example, inline block.accept instead of store the
character to a local var also helps.

Cheers,
Henry