RFR: 8244146: javac changes for JEP 306

[Joe Darcy]

8244146: javac changes for JEP 306

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Commit messages:
 - Add explicit test for warning strictfp suppression.
 - Appease jcheck and enabled strictfp in ConstFold.
 - Follow Jan's suggestion for diagnostics timing.
 - Alternate attempt to get warning suppression working; direct annotations don't work.
 - Checkpoint with initial lint implementation and passing langtools regression tests.
 - Appease jcheck.
 - Add explicit test for strictfp-ness checking for methods and constructors.
 - All langtools regression tests pass; switch to filtering out strictfp bit in ClassWriter.
 - 8244146: javac changes for JEP 306
 - Merge branch 'master' into 8244146
 - ... and 1 more: https://git.openjdk.java.net/jdk/compare/1afbab63...a0a68baa

Changes: https://git.openjdk.java.net/jdk/pull/3831/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3831&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8244146
  Stats: 556 lines in 26 files changed: 520 ins; 7 del; 29 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3831.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3831/head:pull/3831

PR: https://git.openjdk.java.net/jdk/pull/3831