RFR: Classfile signature bang support [v3]

[Chen Liang]

> Support parsing ! signatures in ClassFile API.

Chen Liang has updated the pull request incrementally with one additional commit since the last revision:

  Maurizio reviews

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Changes:
  - all: https://git.openjdk.org/valhalla/pull/1933/files
  - new: https://git.openjdk.org/valhalla/pull/1933/files/335464c6..37617697

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1933&range=02
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1933&range=01-02

  Stats: 26 lines in 4 files changed: 12 ins; 0 del; 14 mod
  Patch: https://git.openjdk.org/valhalla/pull/1933.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1933/head:pull/1933

PR: https://git.openjdk.org/valhalla/pull/1933