RFR: 8311583: tableswitch broken by JDK-8310577

[Coleen Phillimore]

I demoted some types for -Wconversion warnings but they're supposed to be larger types to catch overflow for tableswitch and lookupswitch.  Restored old code (except int64_t not jlong).
Tested with tier1-4.

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

Commit messages:
 - 8311583: tableswitch broken by JDK-8310577

Changes: https://git.openjdk.org/jdk/pull/14788/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14788&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311583
  Stats: 148 lines in 4 files changed: 141 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/14788.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14788/head:pull/14788

PR: https://git.openjdk.org/jdk/pull/14788