RFR: 8335451: Prototype support for an exact integer arithmetic type [v4]

[Joe Darcy]

> The Math class has support for "exact" forms of int and long add, subtract, multiply, and divide that throw exceptions instead of wrapping around in a two's complement sense. This nested class in Integer prototype what adding type-level support for that functionality would look like.

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Improve witness related declarations.

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1937/files
  - new: https://git.openjdk.org/valhalla/pull/1937/files/2e511bab..e64c7588

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1937&range=03
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1937&range=02-03

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/valhalla/pull/1937.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1937/head:pull/1937

PR: https://git.openjdk.org/valhalla/pull/1937