RFR: 8254775: Microbenchmark StringIndexOfChar doesn't compile

[Claes Redestad]

- Illegal use of a unicode codepoint > \uFFFF as a char.
- Wrong class name.
- @Benchmark methods shouldn't be static.

Each of these breaks the build, e.g. make build-microbenchmark fails, so it seems the micro was never tested..?

This patch fixes up the micro so it compiles, but makes no guarantees the micro does anything useful.

-------------

Commit messages:
 - Benchmark methods should be non-static
 - Mismatching name
 - Use a codepoint that fits in a char

Changes: https://git.openjdk.java.net/jdk/pull/661/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=661&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254775
  Stats: 18 lines in 1 file changed: 0 ins; 0 del; 18 mod
  Patch: https://git.openjdk.java.net/jdk/pull/661.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/661/head:pull/661

PR: https://git.openjdk.java.net/jdk/pull/661