RFR: 8255900: x86: Reduce impact when VerifyOops is disabled [v2]

[Claes Redestad]

> - Don't generate stub _verify_oop_subroutine_entry on startup if -VerifyOops
> - Make VerifyOops check in calls to MacroAssembler::verify_oop inlineable. (VerifyOops is a develop flag, so this allows more aggressive code elimination in a few place)
> - (trivial pile-on) remove unused set_word_if_not_zero
> 
> Slightly improves static footprint, gets rid of a stub and reduce jitter during jitting in product builds.

Claes Redestad has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:

 - Revert arm/aarch64 changes
 - Merge branch 'master' into verify_oop_stub
 - Apply similar improvements on arm/aarch64
 - Fix copy-paste error
 - add checked variants of _verify_oop to avoid calls in product builds
 - Merge branch 'master' into verify_oop_stub
 - Cleanup verify_oop

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1058/files
  - new: https://git.openjdk.java.net/jdk/pull/1058/files/0e083d99..5407d476

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1058&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1058&range=00-01

  Stats: 1820 lines in 271 files changed: 737 ins; 712 del; 371 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1058.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1058/head:pull/1058

PR: https://git.openjdk.java.net/jdk/pull/1058