RFR: 8285255: refine StringLatin1.regionMatchesCI_UTF16

[XenoAmess]

some thoughts after watching 8285001: Simplify StringLatin1.regionMatches  https://github.com/openjdk/jdk/pull/8292/

            if (Character.toLowerCase(u1) == Character.toLowerCase(u2)) {
                continue;
            }

should be changed to 

            if (((u1 == c1) ? CharacterDataLatin1.instance.toLowerCase(c1) : c1) == Character.toLowerCase(u2)) {
                continue;
            }

as:

1. c1 is LATIN1, so CharacterDataLatin1.instance.toLowerCase seems faster.
2. because c1 is LATIN1, so if u1 != c1, then c1 is already lowercase, and don't need a lowercase cauculation.

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Commit messages:
 - 9073087: refine StringLatin1.regionMatchesCI_UTF16

Changes: https://git.openjdk.java.net/jdk/pull/8308/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8308&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8285255
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8308.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8308/head:pull/8308

PR: https://git.openjdk.java.net/jdk/pull/8308