RFR: 8178348: left_n_bits(0) invokes undefined behavior

[Harold Seigel]

Please review this small change to remove the unused left_n_bits(n) macro.  This change was regression tested with Mach5 tiers 1 and 2 on Linux, Windows, and Mac OS.

Thanks, Harold

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

Commit messages:
 - 8178348: left_n_bits(0) invokes undefined behavior

Changes: https://git.openjdk.java.net/jdk/pull/2944/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2944&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8178348
  Stats: 5 lines in 2 files changed: 0 ins; 4 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2944.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2944/head:pull/2944

PR: https://git.openjdk.java.net/jdk/pull/2944