RFR: 8293188: x86_64: Introduce stubGenerator_x86_64.hpp [v2]

[Vladimir Ivanov]

> Introduce stubGenerator_x86_64.hpp and extract StubGenerator class declaration there. 
> 
> Testing: hs-tier1 - hs-tier4

Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:

  update

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10111/files
  - new: https://git.openjdk.org/jdk/pull/10111/files/8e33a642..b229fce2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10111&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10111&range=00-01

  Stats: 8 lines in 2 files changed: 6 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10111.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10111/head:pull/10111

PR: https://git.openjdk.org/jdk/pull/10111