RFR: JDK-8296322 javac: use methods to manage parser mode flags [v3]

[Jim Laskey]

> Manage parser mode flags using methods for easy of reading and maintenance.

Jim Laskey has updated the pull request incrementally with one additional commit since the last revision:

  Bring up to date

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10981/files
  - new: https://git.openjdk.org/jdk/pull/10981/files/faf18a62..4e4437cb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10981&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10981&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/10981.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10981/head:pull/10981

PR: https://git.openjdk.org/jdk/pull/10981